Research activity information

• Apr. 2022 Architectural Institute of Japan, AIJ Young Researcher Award 2022, Predicting absorption characteristics of single-leaf permeable membrane absorbers using finite element method in a time domain

  Okuzono Takeshi

  会員により近年中に発表された独創性・萌芽性・将来性のある建築に関する優れた論文等の業績

  Official journal

  共同研究・競争的資金等の業績IDIRI


• Sep. 2012 日本音響学会, 粟屋潔学術奨励賞, スプライン音響要素を用いた時間領域有限要素法の分散誤差低減

  奥園 健


• May 2007 日本建築学会九州支部, 建築九州賞(研究新人賞), 有限要素法による室内音場の時間応答解析－反復解法の選定と小ホール内音場解析－

  奥園 健

• Microslit-embedded acoustic metasurface for bandpass filter shaped sound absorption

  Takeshi Okuzono

  This paper presents a proposal of sub-wavelength acoustic metasurface (AMS) sound absorbers, designated as MeAMS absorbers, with coupled-microslit resonators of gradually decreasing sizes in the respective component resonators. A MeAMS absorber can provide bandpass filter-shaped near-perfect absorption. The prediction theory of the present AMS absorbers is also proposed with two design methods to ascertain the dimensions of respective component resonators. The theory for AMS absorbers composed of single-microslit resonators is first verified with finite element method (FEM) simulation using thermoviscous boundary layer impedance boundary conditions. It is validated further for two 3D printed samples by an impedance tube measurement. Then, the theoretical predictability of absorption characteristics of MeAMS absorbers is discussed via FEM simulations and the impedance tube measurement for three 3D printed samples, revealing that the present theory provides a reasonable approximation of the absorption characteristics of MeAMS absorbers. Two one-third octave band near-perfect absorbers are also presented for practical applications.

  Lead, Acoustical Society of Japan, May 2024, Acoustical Science and Technology, 45(3) (3), 147 - 157, English, International magazine, Co-authored internationally

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Time-domain extended-reaction microperforated panel sound absorber modeling for acoustics simulation by finite element method

  Takumi Yoshida, Takeshi Okuzono, Kimihiro Sakagami

  For precise wave-based room acoustics modeling, an accurate extended-reaction (ER) sound absorber model must be formulated to assess frequency and incident-angle dependences of a sound absorber. Two novel efficient time-marching schemes with implicit time-domain FEM (TD-FEM) are presented to model the extended reacting boundary of microperforated panel (MPP) sound absorbers. Generally, MPP absorbers (MPPAs) have an air cavity behind them, which causes ER behavior. Formulating the ER behavior of MPPAs is necessary for simulating room acoustics. A hindrance to the time-domain modeling of the ER of MPPAs is the need to treat its complex impedance on the microperforations. The proposed schemes model MPPs as interior boundary conditions and deal with the complex transfer impedance with auxiliary differential equations (ADEs), producing stable schemes after the Crank–Nicolson solver is applied. For scheme verification, the impedance tube model with a single-leaf MPPA is analyzed. Additionally, the effectiveness of the proposed schemes is assessed by practical room acoustics modeling involving MPPAs and comparison with a frequency-domain FEM solver, which can address complex transfer impedance exactly. The results show excellent performance of the proposed methods. The TD-FEMs can model room acoustics, including the MPPA, O(100) times faster while maintaining accuracy comparable to that of FD-FEM.

  Corresponding, Acoustical Society of Japan, Mar. 2024, Acoustical Science and Technology, 45(2) (2), 57 - 68, English, International magazine

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Computational Accuracy and Efficiency of Room Acoustics Simulation Using a Frequency Domain FEM with Air Absorption: 2D Study

  Takeshi Okuzono

  Recently, to simulate sound propagation inside architectural spaces at high frequencies, the application of computationally expensive wave-based numerical methods to room acoustics simulation is increasing gradually. Generally, standard room acoustics simulations in the frequency domain are performed based on the lossless Helmholtz equation. However, for acoustics simulation at high frequencies, consideration of the sound attenuation effect caused by air absorption is an aspect to increase the reliability of predictions. Although a simple approach based on the lossy Helmholtz equation is available to include the air absorption effect in the frequency domain, its accuracy and efficiency are still not discussed well. This paper presents an accuracy and efficiency estimation of FEM based on the lossy Helmholtz equation via two numerical problems in two dimensions: a plane wave propagation problem up to 20 kHz in a long duct with 1 km length and a sound propagation problem in a real-scale office up to 6 kHz. Results revealed that the lossy Helmholtz equation-based FEM can include the air absorption effect accurately up to 20 kHz. Moreover, a possibility of providing a higher computational efficiency at higher frequencies is suggested when the magnitude of the pure-tone sound attenuation coefficient is large.

  Lead, Dec. 2023, Applied Sciences, English, International magazine

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• A pilot study on the sound insulation performance of plenum doors

  Kimihiro Sakagami, Haruhi Inoue, Takeshi Okuzono

  Demands for natural ventilation is inaugurated recently, particularly after the COVID-19 outbreak. Various ventilating windows have been proposed, one of which a plenum window has been studied for these years. Since the COVID outbreak shops and restaurants often leave doors opened for ventilation reasons during their business hours. However, by this, the indoor sound environment is suffered by incoming noises from streets. Therefore, it is desirable that a sound insulation structure enabling natural ventilation is developed. In this study, we propose a door with plenum structure which is an application of the same principle of plenum windows to a door. Doors and windows are of different sizes, and under different conditions. Therefore, in this paper, as a pilot study, we employed finite element method to analyse the sound insulation characteristics of a plenum door. Results show that a plenum door, although its sound insulation is not very high, shows sound insulation performance to a certain extent. Also, a parametric study is given to show the effect of parameters including that of sound absorption linings.

  Institute of Noise Control Engineering (INCE), Nov. 2023, INTER-NOISE and NOISE-CON Congress and Conference Proceedings, 268(2) (2), 6318 - 6327, English

  [Refereed]

  Scientific journal


• Basic study of practical prediction of sound insulation performance of double-glazed window

  Yohei Tsukamoto, Kaoru Tamai, Kimihiro Sakagami, Takeshi Okuzono

  Since double-glazed glasses have superior thermal insulation performance compared to single-glazed glasses, they are widely employed for windows in recent buildings. However, the double-glazed glasses used in general buildings have mass-air-mass resonance at around 200-400 Hz, and, at those frequencies, their sound reduction indices are often lower than that of single-glazed glasses that have the same weight. In designing an indoor acoustic environment, it is helpful to have a practical method to predict the sound reduction index of a double-glazed glass window, including the resonance. In this study, at first, measured values of actual double-glazed windows are compared with calculated values of the existing sound transmission theories for double plates and applicability of the theories to double-glazed windows are investigated. Next, in order to obtain a practical prediction of the sound reduction indices of double-glazed windows, some measured values of double-glazed windows are collected from a manufacturer's database and the characteristics of the sound reduction indices are discussed.

  Institute of Noise Control Engineering (INCE), Nov. 2023, INTER-NOISE and NOISE-CON Congress and Conference Proceedings, 268(7) (7), 1297 - 1307, English

  [Refereed]

  Scientific journal


• Acoustic simulation using a frequency domain FEM with air absorption

  Takeshi Okuzono, Takumi Yoshida

  Recently, the applicability of wave-based acoustic simulations that solve the Helmholtz equation has been expanding drastically to high-frequency ranges and large spaces with the development of higher efficient methods. Although standard acoustic simulations generally solve the lossless Helmholtz equation, considering the air absorption effect will contribute to increasing prediction accuracy at higher frequencies. This paper presents an accuracy and efficiency assessment of frequency-domain FEM (FD-FEM) acoustic simulations with air absorption effect based on the ISO 9613-1 model. First, the accuracy of FD-FEM, including the air absorption model, is verified at frequencies up to 20 kHz via a plane wave propagation problem in a long duct. Then, we will demonstrate its efficiency via a real-scale 2D office problem. Results reveal that considering air absorption can increase computational efficiency for higher frequencies as an additional benefit.

  Lead, Institute of Noise Control Engineering (INCE), Nov. 2023, INTER-NOISE and NOISE-CON Congress and Conference Proceedings, 268(8) (8), 874 - 879, English

  [Refereed][Invited]

  International conference proceedings


• An auditory virtual reality of meeting room acoustics using wave-based acoustic simulations: A content for intuitive understanding of room-acoustics control effect by sound absorbers

  Kazuha Okazawa, Takeshi Okuzono, Takumi Yoshida

  Recently, wave-based room acoustic simulation technologies are becoming a realistic option as a small-room acoustics design tool and a virtual indoor sound environment creation tool for research and education. The present paper shows an auditory VR meeting room content, which makes us easily understand how sound absorbers play an essential role in creating a better acoustic environment. Unity creates the 3D virtual reality model, and a binaural room-acoustic auralization is realized by a hybrid technique combined with Ambisonics and the head-related transfer function using RIRs computed by a high-speed parallel wave-based room acoustics solver. The VR meeting room is constructed under various acoustic treatments with sound absorber modeling by wave-based material models.

  Corresponding, Institute of Noise Control Engineering (INCE), Nov. 2023, INTER-NOISE and NOISE-CON Congress and Conference Proceedings, 268(2) (2), 6328 - 6335, English

  [Refereed]

  International conference proceedings


• A high-order explicit time-domain FEM using 15-node tetrahedral elements for room acoustics modeling: Basic performance

  Takumi Yoshida, Takeshi Okuzono, Kimihiro Sakagami

  Time-domain room acoustic modeling using mass-lumped higher-order tetrahedral finite elements with an explicit time-marching scheme is highly attractive because of its excellent geometrical flexibility with unstructured meshing and applicability into massively parallel computing. However, the standard mass-lumped tetrahedral elements yield an unstable scheme, and only implicit time-marching schemes are available. This study proposes a novel wave-based room acoustics solver based on a high-order explicit time-domain FEM. The present solver uses mass-lumped 15-node tetrahedral elements for spatial discretization and a dissipation-free two-stage partitioned Runge-Kutta time integration for time discretization. The 15-node tetrahedral elements had been developed to apply mass-lumping methods to 10-node tetrahedral elements, which are the most common finite element in engineering applications, but its applicability in room acoustics problems is unknown. Higher accuracy and efficiency of the proposed method over the standard method using 10-node tetrahedral elements is presented through an eigenvalue analysis of a long duct model and acoustic simulations in a small room. Additionally, frequency-dependent sound absorbing boundary is implemented by revising an auxiliary differential equation method.

  Institute of Noise Control Engineering (INCE), Nov. 2023, INTER-NOISE and NOISE-CON Congress and Conference Proceedings, 268(3) (3), 5251 - 5261, English

  [Refereed][Invited]

  International conference proceedings


• Binaural Auralization of Room Acoustics with a Highly Scalable Wave-Based Acoustics Simulation

  Takumi Yoshida, Takeshi Okuzono, Kimihiro Sakagami

  This paper presents a proposal of an efficient binaural room-acoustics auralization method, an essential goal of room-acoustics modeling. The method uses a massively parallel wave-based room-acoustics solver based on a dispersion-optimized explicit time-domain finite element method (TD-FEM). The binaural room-acoustics auralization uses a hybrid technique of first-order Ambisonics (FOA) and head-related transfer functions. Ambisonics encoding uses room impulse responses computed by a parallel wave-based room-acoustics solver that can model sound absorbers with complex-valued surface impedance. Details are given of the novel procedure for computing expansion coefficients of spherical harmonics composing the FOA signal. This report is the first presenting a parallel wave-based solver able to simulate room impulse responses with practical computational times using an HPC cloud environment. A meeting room problem and a classroom problem are used, respectively, having 35 million degrees of freedom (DOF) and 100 million DOF, to test the parallel performance of up to 6144 CPU cores. Then, the potential of the proposed binaural room-acoustics auralization method is demonstrated via an auditorium acoustics simulation of up to 5 kHz having 750,000,000 DOFs. Room-acoustics auralization is performed with two acoustics treatment scenarios and room-acoustics evaluations that use an FOA signal, binaural room impulse response, and four room acoustical parameters. The auditorium acoustics simulation showed that the proposed method enables binaural room-acoustics auralization within 13,000 s using 6144 cores.

  Corresponding, MDPI AG, Feb. 2023, Applied Sciences, 13(5) (5), 2832 - 2832, English, International magazine

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• High potential of small-room acoustic modeling with 3D time-domain finite element method

  Takeshi Okuzono, Takumi Yoshida

  Applicability of wave-based acoustics simulation methods in the time domain has increased markedly for performing room-acoustics simulation. They can incorporate sound absorber effects appropriately with a local-reaction frequency-dependent impedance boundary condition and an extended-reaction model. However, their accuracy, efficiency and practicality against a standard frequency-domain solver in 3D room acoustics simulation are still not known well. This paper describes a performance examination of a recently developed time-domain FEM (TD-FEM) for small-room acoustics simulation. This report first describes the significantly higher efficiency of TD-FEM against a frequency-domain FEM (FD-FEM) via acoustics simulation in a small cubic room and a small meeting room, including two porous-type sound absorbers and a resonant-type sound absorber. Those sound absorbers are modeled with local-reaction frequency-dependent impedance boundary conditions and an extended-reaction model. Then, the practicality of time-domain FEM is demonstrated further by simulating the room impulse response of the meeting room under various sound absorber configurations, including the frequency component up to 6 kHz. Results demonstrated the high potential and computational benefit of time-domain FEM as a 3D small room acoustics prediction tool.

  Lead, Frontiers Media {SA}, Dec. 2022, Frontiers in Built Environment, 8, English, Domestic magazine

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Basic study of practical prediction of sound insulation performance of double window

  Yohei Tsukamoto, Kaoru Tamai, Kimihiro Sakagami, Takeshi Okuzono, Yoshihiro Tomikawa

  Acoustical Society of Japan, Nov. 2022, Acoustical Science and Technology, 43(6) (6), 335 - 338, English, International magazine

  [Refereed]

  Scientific journal


• Classification of ground states using airborne hyper- spectral imagery for wide-area prediction of noise propagation

  Yumi Kurosaka, Takuya Oshima, Yasuhiro Hiraguri, Takeshi Okuzono

  地表面音響特性の広域における空間分布データは，未整備である。そこで，ハイパスペクトル航空画像を用いて地表面をその音響特性に応じて分類する手法を開発する。3 季節に複数種の地表面の音響特性を測定し，実効的流れ抵抗を推定して地表面の状態の分類クラスを決める。教師付き分類手法のMED-SD法を用い，教師スペクトルと適用する画像の撮影季節を12パターンに組み合わせ，分類精度を評価する。最 後に，886 m × 445 mの範囲を分類する。その結果，秋に撮影した航空画像から求めた教師スペクトルが最も分類に適した。これにより，広域の地表面の音響特性を実際の状態に基づき，的確かつ効率的に設定できる可能性が示された。

  Nov. 2022, 日本音響学会誌, 78(11) (11), 635 - 645, Japanese, Domestic magazine

  [Refereed]

  Scientific journal


• Designable heterogeneous MPPs and their applications

  Kimihiro SAKAGAMI, Midori KUSAKA, Takeshi OKUZONO

  Oct. 2022, PROCEEDINGS of the 24th International Congress on Acoustics, ABS-0375, English, International magazine

  [Refereed][Invited]


• Massively Parallel Wave-Based Room Acoustic Solver with DDM Based Explicit FEM

  Takumi Yoshida, Takeshi Okuzono, Kimihiro Sakagami

  Oct. 2022, PROCEEDINGS of the 24th International Congress on Acoustics, ABS-0482, English, International magazine

  [Refereed][Invited]


• A time-domain FEM for wave-based room acoustic simulations: Acoustic modeling of a meeting room with various sound absorber configurations

  Takeshi OKUZONO, Takumi YOSHIDA, Kimihiro SAKAGAMI

  Lead, Oct. 2022, PROCEEDINGS of the 24th International Congress on Acoustics, ABS-0099, English, International magazine

  [Refereed][Invited]

  International conference proceedings


• Sound insulation characteristics of small fixed windows in a laboratory and prediction with an existing theory

  Marie Mimura, Yohei Tsukamoto, Yoshihiro Tomikawa, Takeshi Okuzono, Kimihiro Sakagami

  Acoustical Society of Japan, Sep. 2022, Acoustical Science and Technology, 43(5) (5), 276 - 279, English, International magazine

  [Refereed]

  Scientific journal


• Finite element modeling for predicting sound insulation of fixed windows in a laboratory environment

  Marie Mimura, Takeshi Okuzono, Kimihiro Sakagami

  This paper presents discussion of the prediction capability of three numerical models using finite element method for predicting the sound reduction index (SRI) of fixed windows having different dimensions in a laboratory environment. The three numerical models tested here only discretize the window part or windows part and the space around the windows to reduce the necessary computational cost for vibroacoustics simulations. An ideal diffused sound incidence condition is assumed for three models. Their predictability and numerical efficiency were examined over five fixed windows with different dimensions compared to measured SRIs. First, the accuracy of the simplest model in which the window part is only discretized with finite elements was examined. Acoustic radiation to the transmission field is computed using Rayleigh’s integral. Calculations were performed under two loss factor setups respectively using internal loss factors of each material and measured total loss factor of each window. The results were then compared with the measured values. Results revealed the effectiveness of using the measured total loss factor at frequencies around and above the coincidence frequencies. Subsequently, we tested the prediction accuracy of a numerical model that includes a niche existing in a laboratory environment. Also, hemispherical free fields around the window are discretized using fluid elements and infinite fluid elements. The results underscored the importance of including a niche in a numerical model used to predict sound reduction index below 1 kHz for smaller windows accurately. Nevertheless, this numerical model, including a niche, entails high computational costs. To enhance the prediction efficiency, we examined the applicability of a weak-coupling model that divides calculation procedures into three steps: (1) incidence field calculation to the window surface, (2) sound transmission calculation in fixed windows, and (3) sound radiation calculation from a window surface to a transmission field. Results revealed that the weak-coupling model produces almost identical results to those of a strong-coupling model, but with higher efficiency.

  Corresponding, Frontiers Media SA, Aug. 2022, Frontiers in Built Environment, 8, 971459, English, International magazine

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• A Basic Study on the Design of Dotted-Art Heterogeneous MPP Sound Absorbers

  Kimihiro Sakagami, Midori Kusaka, Takeshi Okuzono

  Recently, dotted-art MPPs have been proposed in which a designed pattern is made with the holes. In such a case, the MPP becomes heterogeneous in general. However, existing theories used for the prediction of the absorption characteristics of MPPs assume homogeneity. Therefore, the elaboration of a method for heterogeneous MPPs needs to be performed. In previous work, the authors proposed a method to predict the absorption characteristics of a heterogeneous MPP by using synthesized impedances of each part with different parameters; this is called the synthetic impedance method (SIM) in the present paper. The SIM can potentially be used for various heterogeneous MPPs; however, its scope of applicability needs to be clarified. Furthermore, in proposing a design concept of dotted-art heterogeneous MPPs, the condition that would make the designed MPPs fall within the scope of the SIM needs to be determined. Therefore, in this study, in order to clarify the scope of the applicability of the SIM, twelve samples are first prepared, and then measured sound absorption characteristics and predicted ones are compared and examined in terms of prediction errors. The results show that there are two conditions that should be met to produce predictable heterogeneous MPPs: (1) holes are distributed over the entire surface of the specimen, and (2) the hole spacing is constant. Considering these conditions, a design concept for a dotted-art heterogeneous MPP is proposed: two types of holes, larger holes for the pattern and smaller holes for the background, should be used to meet the above two conditions. Case studies with nine prototypes show that the SIM can make predictions for dotted-art heterogeneous MPPs fabricated according to the concept described above.

  MDPI AG, Jul. 2022, Acoustics, 4(3) (3), 588 - 608

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• A Parallel Dissipation-Free and Dispersion-Optimized Explicit Time-Domain FEM for Large-Scale Room Acoustics Simulation

  Takumi Yoshida, Takeshi Okuzono, Kimihiro Sakagami

  Wave-based acoustics simulation methods such as finite element method (FEM) are reliable computer simulation tools for predicting acoustics in architectural spaces. Nevertheless, their application to practical room acoustics design is difficult because of their high computational costs. Therefore, we propose herein a parallel wave-based acoustics simulation method using dissipation-free and dispersion-optimized explicit time-domain FEM (TD-FEM) for simulating room acoustics at large-scale scenes. It can model sound absorbers with locally reacting frequency-dependent impedance boundary conditions (BCs). The method can use domain decomposition method (DDM)-based parallel computing to compute acoustics in large rooms at kilohertz frequencies. After validation studies of the proposed method via impedance tube and small cubic room problems including frequency-dependent impedance BCs of two porous type sound absorbers and a Helmholtz type sound absorber, the efficiency of the method against two implicit TD-FEMs was assessed. Faster computations and equivalent accuracy were achieved. Finally, acoustics simulation of an auditorium of 2271 m3 presenting a problem size of about 150,000,000 degrees of freedom demonstrated the practicality of the DDM-based parallel solver. Using 512 CPU cores on a parallel computer system, the proposed parallel solver can compute impulse responses with 3 s time length, including frequency components up to 3 kHz within 9000 s.

  Corresponding, MDPI AG, Jan. 2022, Buildings, 12(2) (2), 105 - 105, English, International magazine

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• On the Robustness and Efficiency of the Plane-Wave-Enriched FEM with Variable q-Approach on the 2D Room Acoustics Problem

  Shunichi Mukae, Takeshi Okuzono, Kimihiro Sakagami

  Partition of unity finite element method with plane wave enrichment (PW-FEM) uses a shape function with a set of plane waves propagating in various directions. For room acoustic simulations in a frequency domain, PW-FEM can be an efficient wave-based prediction method, but its practical applications and especially its robustness must be studied further. This study elucidates PW-FEM robustness via 2D real-scale office room problems including rib-type acoustic diffusers. We also demonstrate PW-FEM performance using a sparse direct solver and a high-order Gauss–Legendre rule with a recently developed rule for ascertaining the number of integration points against the classical linear and quadratic FEMs. Numerical experiments investigating mesh size and room geometrical complexity effects on the robustness of PW-FEM demonstrated that PW-FEM becomes more robust at wide bands when using a mesh in which the maximum element size maintains a comparable value to the wavelength of the upper-limit frequency. Moreover, PW-FEM becomes unstable with lower spatial resolution mesh, especially for rooms with complex shape. Comparisons of accuracies and computational costs of linear and quadratic FEM revealed that PW-FEM requires twice the computational time of the quadratic FEM with a mesh having spatial resolution of six elements per wavelength, but it is highly accurate at wide bands with lower memory and with markedly fewer degrees of freedom. As an additional benefit of PW-FEM, the impulse response waveform of quadratic FEM in a time domain was found to deteriorate over time, but the PW-FEM waveform can maintain accurate waveforms over a long time.

  Corresponding, MDPI AG, Jan. 2022, Acoustics, 4(1) (1), 53 - 73, English, International magazine

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Pilot study on numerical prediction of sound reduction index of double window system: Comparison of finite element prediction method with measurement

  Marie Mimura, Takeshi Okuzono, Kimihiro Sakagami

  The development of windows with high sound insulation performance is essential for preventing the infiltration of traffic noise and the leakage of room noise. A numerical prediction is an effective means of reducing sound insulation testing and development costs to develop a quietness window. As a numerical prediction method for the sound reduction index, the finite element method (FEM) is useful in dealing with structure-acoustic problems. This study was conducted as a pilot study toward developing an accurate numerical model to predict the sound reduction index of a double window. We discussed the accuracy of an FEM model for predicting the diffuse incidence sound reduction index of double windows through a comparison with measured values for a simplified realistically scaled double window. The FE results were compared with measured ones for eight cases with and without a frame absorber. Results showed that the best match to measured values is obtained when using a frame absorber in all the perimeters inside the air cavity. Also, a better agreement is obtained at frequencies of 160–2,000Hz in other cases. However, a marked discrepancy is found at frequencies above 2,000Hz and below 160Hz. Possible reasons for the discrepancies are also discussed.

  Acoustical Society of Japan, Jan. 2022, Acoustical Science and Technology, 43(1) (1), 32 - 42, English, International magazine

  [Refereed]

  Scientific journal


• Modeling microperforated panels and permeable membranes for a room acoustic solver with plane-wave enriched FEM

  Shunichi Mukae, Takeshi Okuzono, Kanako Tamaru, Kimihiro Sakagami

  Plane-wave-enriched finite element method (FEM), an efficient wave-based prediction method, uses shape functions incorporating a set of plane waves propagating in various directions to enhance the sound field approximation capability. The method can be an efficient wave-based acoustic solver for room acoustic simulations because it can simulate wave phenomena in rooms accurately with markedly fewer finite elements in spatial discretization than those used for standard FEM. However, several aspects remain to be addressed before its use for practical room acoustic simulations. Accurate sound absorber modelings able to address their frequency and incident angle dependence of absorption characteristics present extremely important issues. This paper presents a proposal of a method of implementing an extended-reaction model of microperforated panel (MPP) and permeable membrane (PM) sound absorbers into a room acoustic solver with plane-wave-enriched FEM. First, we demonstrate the validity of the proposed method in comparison with theoretical values in which impedance tube problems including three sound absorbers composed of MPP and PM are used. Then, the effectiveness over standard FEM is demonstrated via 2D real-scale office problems with the three MPP-PM sound absorbers.

  Corresponding, Elsevier BV, Jan. 2022, Applied Acoustics, 185, 108383 - 108383, English, International magazine

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Basic study of practical prediction of sound insulation performance of single-glazed window

  Yohei Tsukamoto, Kaoru Tamai, Kimihiro Sakagami, Takeshi Okuzono, Yoshihiro Tomikawa

  Acoustical Society of Japan, Nov. 2021, Acoustical Science and Technology, 42(6) (6), 350 - 353, English, International magazine

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Efficiency of room acoustic simulations with time-domain FEM including frequency-dependent absorbing boundary conditions: Comparison with frequency-domain FEM

  Takeshi Okuzono, Takumi Yoshida, Kimihiro Sakagami

  Recent wave-based room acoustic simulations in the time domain can incorporate frequency-dependent absorbing boundary conditions (BCs), by which time responses including a broad frequency component are calculable with a single computational run. However, their performance over the frequency-domain method remains poorly understood. This paper presents a discussion of the capabilities of a recently developed implicit time-domain finite element method (TD-FEM) for room acoustics simulation by comparison with a fourth-order accurate frequency-domain FEM (FD-FEM). First, the implicit TD-FEM accuracy is examined via an impedance tube problem, having frequency-dependent absorbing BCs at the tube end, where a specific acoustic admittance ratio of rigidly backed porous sound absorbers is imposed. Results indicate that the implicit TD-FEM has the same solution convergence rate as that of FD-FEM. The solution converges to the FD-FEM solution when using a sufficiently small time interval. A performance comparison of both methods is then made using two real-scale 2D room acoustic problems in an office room and a complexly shaped concert hall. Numerical results show that the implicit TD-FEM can be useful for acoustic simulation in practical-sized rooms at broad frequency ranges with markedly smaller computational costs than those of FD-FEM while maintaining similar accuracy.

  Elsevier BV, Nov. 2021, Applied Acoustics, 182, 108212 - 108212, English, International magazine

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Dissipation-free and dispersion-optimized explicit time-domain finite element method for room acoustic modeling

  Takumi Yoshida, Takeshi Okuzono, Kimihiro Sakagami

  This paper presents a proposal for an efficient room acoustic solver with dissipation-free and dispersion-optimized explicit time-domain FEM (TD-FEM), with investigation of its applicability for broadband room acoustic modeling from three numerical experiments. Recently, FEM-based room acoustic solvers have attracted great attention because of their strength in handling complex geometries. However, the development of higher-efficiency solvers is unavoidable to perform acoustic modeling of real-size rooms at kilohertz frequency with small discretization error: the dispersion error. The present paper first formulates a novel room acoustic solver with dissipation-free fourth-order accurate explicit TD-FEM using a three-step time integration method. A dispersion-optimized solver is further proposed in which dispersion error is minimized in the axial and diagonal directions at a specific frequency under given spatial resolution mesh or elements, by which the approximation capability at higher frequencies is enhanced without any additional computational cost. The performance of the optimized solver in broadband acoustic simulation using cubic elements is then examined in comparison with the original fourth-order accurate solver and the standard implicit TD-FEM. Finally, higher efficiency of the optimized solver is also demonstrated for acoustic simulation in a larger rectangular room discretized with rectangular and distorted hexahedral elements.

  Acoustical Society of Japan, Sep. 2021, Acoustical Science and Technology, 42(5) (5), 270 - 281, English, International magazine

  [Refereed]

  Scientific journal


• Exploration of efficient numerical integration rule for wideband room-acoustics simulations by plane-wave-enriched finite-element method

  Kanako Tamaru, Takeshi Okuzono, Shunichi Mukae, Kimihiro Sakagami

  In this study, we assessed the reduction in the computational costs of a room-acoustics solver by the partition of unity finite-element method (PUFEM), particularly addressing the element matrix construction process with numerical integration rules. The PUFEM enriches the approximation of sound fields by incorporating a general solution of the Helmholtz equation into shape functions. Plane wave enrichment is applied herein. In plane-wave-enriched FEM, the construction of element matrices using a high-order Gauss–Legendre quadrature is the main numerical operation with a long computational time. To reduce the computational time of the room-acoustics solver with plane-wave-enriched FEM, in this report, we describe our exploration of efficient integration rules via an ideal plane wave propagation problem in a duct. We present two integration rules: a well-used existing rule extended to the low-frequency range and another derived by the linear regression of the relationship between the number of wavelengths included in each element and the minimum number of integration points required for solution convergence. Numerical results revealed that both rules produce accurate frequency responses in a broad frequency range. However, the rule obtained by linear regression outperforms the extended rule.

  Acoustical Society of Japan, Sep. 2021, Acoustical Science and Technology, 42(5) (5), 231 - 240, English, International magazine

  [Refereed]

  Scientific journal


• An explicit time-domain FEM for acoustic simulation in rooms with frequency-dependent impedance boundary: Comparison of performance in 2D simulation with frequency-domain FEM

  Takumi Yoshida, Takeshi Okuzono, Yui Sugimoto, Kimihiro Sakagami

  Accurate boundary modelings that address the frequency-dependent sound absorption characteristics of various sound absorbers are crucial for wave-based room acoustic simulation. In time-domain simulations, however, a computationally demanding convolution appears in frequency-dependent impedance boundary conditions. The present paper proposes a room acoustic solver with a fourth-order accurate explicit TD-FEM, incorporating a frequency-dependent absorbing boundary condition efficiently using a recursive convolution method, namely the auxiliary differential equation (ADE) method. Its performance against the fourth-order accurate frequency-domain FEM is examined via 2D real-scale room acoustic problems, solving a sound propagation in an office room up to 4.5 kHz. Firstly, we describe briefly the formulation of the proposed room acoustics solver based on the explicit TD-FEM. Then, the discretization error property of the proposed method is evaluated via an impedance tube problem, including a frequency-dependent impedance boundary of porous sound absorber. Finally, the accuracy and efficiency of the proposed method are demonstrated with the comparison of frequency-domain FEM solver, which uses a sparse direct solver for the solution of the linear system at each frequency. Results showed the proposed method can perform an acoustic simulation with significantly low computational costs compared to the frequency-domain solver while keeping an acceptable level of accuracy.

  Institute of Noise Control Engineering (INCE), Aug. 2021, INTER-NOISE and NOISE-CON Congress and Conference Proceedings, InterNoise21, 263(5) (5), 1120 - 1129, English

  [Refereed]

  International conference proceedings


• Application of transparent microperforated panels to acrylic partitions for desktop use: A case study by prototyping

  Kimihiro Sakagami, Midori Kusaka, Takeshi Okuzono, Shigeyuki Kido, Daichi Yamaguchi

  There are various measures currently in place to prevent the spread of coronavirus (COVID-19); however, in some cases, these can have an adverse effect on the acoustic environment in buildings. For example, transparent acrylic partitions are often used in eating establishments, meeting rooms, offices, etc., to prevent droplet infection. However, acrylic partitions are acoustically reflective; therefore, reflected sounds may cause acoustic problems such as difficulties in conversation or the leakage of conversation. In this study, we performed a prototyping of transparent acrylic partitions to which a microperforated panel (MPP) was applied for sound absorption while maintaining transparency. The proposed partition is a triple-leaf acrylic partition with a single acrylic sheet without holes between two MPP sheets, as including a hole-free panel is important to prevent possible droplet penetration. The sound absorption characteristics were investigated by measuring the sound absorption in a reverberation room. As the original prototype showed sound absorption characteristics with a gentle peak and low values due to the openings on the periphery, it was modified by closing the openings on the top and sides. The sound absorption performance was improved to some extent when the top and sides were closed, although there remains the possibility of further improvement. For this study, only the sound absorption characteristics were examined in the prototype experiments. The effects during actual use will be the subject of future study.

  UCL Press, Jul. 2021, UCL Open Environment, 2

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• A Basic Study on the Absorption Properties and Their Prediction of Heterogeneous Micro-Perforated Panels: A Case Study of Micro-Perforated Panels with Heterogeneous Hole Size and Perforation Ratio

  Midori Kusaka, Kimihiro Sakagami, Takeshi Okuzono

  Micro-perforated panels (MPPs) are one of the most promising alternatives to conventional porous sound-absorbing materials. Traditionally, the theory of the sound absorption properties of MPPs is based on the assumption that MPPs are a homogeneous material with identical pores at regular intervals. However, in recent years, some MPPs have not met these conditions, and although a variety of designs have been created, their properties and prediction methods were studied in only fewer works. In this paper, considering the wide variety of MPP designs, we made a trial production of heterogeneous MPPs, which are MPPs with holes of different diameters, and studied the prediction method applicable to these MPPs. We measured the normal incidence sound absorption characteristics of those MPPs, backed by a rigid backing and air-cavity in-between, in an impedance tube. The prediction method proposed in this work is to treat the heterogeneous MPPs as combinations of several homogeneous components, and to combine them after applying the existing theory on homogeneous MPPs to each component. As a result, except in a few cases, the measured and predicted values of the absorption properties agreed relatively well. We also found that the arrangement of the holes in the material and the depth of the back cavity affected the agreement between the measured and predicted results.

  MDPI AG, Jul. 2021, Acoustics, 3(3) (3), 473 - 485, English, International magazine

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• PERFORMANCE OF A DISPERSION-OPTIMIZED EXPLICIT FEM IN ROOM ACOUSTIC SIMULATIONS INCLUDING IMPEDANCE BOUNDARIES

  Takumi Yoshida, Takeshi Okuzono, Kimihiro Sakagami

  The development of a computationally efficient wave-based room acoustic solver is an active re- search area in the architectural acoustics field, thanks to both the progress in computational technology and attractiveness for accurate acoustic modeling in virtual spaces. The authors have been proposed an efficient acoustic solver with fourth-order accurate explicit FEM using a dispersion-reduced low-order element and a modified time integration and shown its applicability to real-scale room acoustic modeling up to several kilohertz. However, the method has the drawback of having a dissipation property. The present paper proposes dissipation-free explicit FEMs for acoustic simulations to overcome the draw- back. We also present the dispersion-optimized method that can produce an accurate result at a high frequency. As a numerical demonstration of the two proposed methods’ effectiveness, we show that the developed two acoustic solvers have higher accuracy and efficiency than the standard implicit FEM via acoustic simulations in a cubic room with impedance boundaries.

  Silesian University Press, Gliwice, Poland, Jul. 2021, Proceedings of the 27th International Congress on Sound and Vibration, No.1397, 1 - 8, English, International magazine

  [Refereed]

  International conference proceedings


• Basic considerations on the practical method for predicting sound insulation performance of a single-leaf window

  Yohei Tsukamoto, Kimihiro Sakagami, Takeshi Okuzono, Yoshihiro Tomikawa

  As a basic study of a practical method for predicting the sound insulation performance of windows, this report presents a study of the sound reduction index of windows with single glazing, below a critical frequency. First, the results calculated by an existing theory for a single plate for the sound reduction indices are compared with measured results of actual windows to assess the theory’s applicability for evaluating the sound insulation performance of windows. Then, a regression analysis is employed to measure the results of a certain number of actual windows to explore a further development of a more practical prediction. The following findings were obtained: (1) Sound reduction indices of actual fixed windows are predictable using Sewell’s transmission theory for a single plate. However, sound reduction indices of openable windows, especially those of sliding windows, are strongly affected by gaps in the window frame. Therefore, predicting sound reduction indices of all windows accurately is difficult if using only one theory. (2) The frequency slope of the window reduction index is much lower than that of the mass law. Regression analyses indicate that the frequency slope of the reduction index of all examined windows is 3.0 dB per octave, on average.

  UCL Press, May 2021, UCL Open Environment, 2

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Some considerations on the use of space sound absorbers with next-generation materials reflecting COVID situations in Japan: additional sound absorption for post-pandemic challenges in indoor acoustic environments

  Kimihiro Sakagami, Takeshi Okuzono

  In this study, we first point out the possible acoustic problems associated with the post-pandemic operation of built environments. In particular, we focus on the problem of acoustic deficiency due to the lack of absorption. This deficiency, which is likely to be encountered in most enclosed spaces in a range of establishments, is due to the reduced number of audience members or users of the space as a result of social distancing. As one of the promising solutions to this problem, we introduce a sound absorption technique using three-dimensional (3D) space sound absorbers developed through our recent research projects. Significantly, the type of sound absorber proposed herein is made of materials that are especially suited to hygiene considerations. The materials are microperforated panels (MPPs) and permeable membranes (PMs), both of which are easily washable and sanitised. Furthermore, we point out that 3D-MPP or PM space absorbers possess the additional value of aesthetic designability.

  UCL Press, Nov. 2020, UCL Open Environment, (1) (1), 1 - 10

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Time-domain finite element formulation of porous sound absorbers based on an equivalent fluid model

  Takumi Yoshida, Takeshi Okuzono, Kimihiro Sakagami

  Acoustical Society of Japan, Nov. 2020, Acoustical Science and Technology, 41(6) (6), 837 - 840, English, International magazine

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Implementation of a frequency-dependent impedance boundary model into a room acoustic solver with time-domain finite element method

  Takumi Yoshida, Takeshi Okuzono, Kimihiro Sakagami

  Acoustical Society of Japan, Nov. 2020, Acoustical Science and Technology, 41(6) (6), 819 - 822, English, International magazine

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Diffuse-field sound absorption characteristics of a spherical-microperforated space absorber

  Kimihiro Sakagami, Midori Kusaka, Takeshi Okuzono, Shigeyuki Kido, Daichi Yamaguchi

  Acoustical Society of Japan, Sep. 2020, Acoustical Science and Technology, 41(5) (5), 784 - 787, English, International magazine

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Three-dimensional MPP space absorbers: An overview of the project and recent development

  Midori Kusaka, Kimihiro Sakagami, Takeshi Okuzono, Shigeyuki Kido, Daichi Yamaguchi

  A micro-perforated panel (MPP) is one of the most promising alternatives of absorbers for its durability, designability, and eco-friendliness. It is typically used with a rigid wall and air-layer between them, forming a Helmholtz resonator. However, this type can be used in limited situations. In order to use it more widely, various MPP space absorbers without any backing structures have been proposed. We proposed three-dimensional MPP absorbers (3-D MPA), i.e., a cylindrical and a rectangular MPP space absorber (CMSA and RMSA), which are superior to other absorbers in terms of wide possibility of arrangement: they can be suspended from the ceiling, or put on the floor. To make 3-D MPA useful for much wider range of applications, a trial production of a spherical MPP space absorber (SMSA) is made. In this paper, as a background the main results of CMSA and RMSA are overviewed. Then, the absorption characteristics of SMSA are measured in a reverberation chamber, and compared with those of CMSA and RMSA. As a result, SMSA shows a resonance peak at around 400 Hz: it is higher than CMSA and RMSA. The results show an SMSA can be used as a space sound absorber in practical situations.

  Korean Society of Noise and Vibration Engineering, Aug. 2020, Proceedings of 2020 International Congress on Noise Control Engineering, INTER-NOISE 2020, English

  International conference proceedings


• The Effect of Deviation Due to the Manufacturing Accuracy in the Parameters of an MPP on Its Acoustic Properties: Trial Production of MPPs of Different Hole Shapes Using 3D Printing

  Kimihiro Sakagami, Midori Kusaka, Takeshi Okuzono, Shinsuke Nakanishi

  In this study, we discuss the effect of the manufacturing accuracy of a microperforated panel (MPP) produced by 3D printers on acoustic properties through measured and calculated results as a pilot study. The manufacturing costs of MPPs have long been one of their shortcomings; however, with recent developments in the manufacturing process, low-cost MPPs are now available. In a further attempt at reducing the cost, 3D printing techniques have recently been considered. Cases of trial production of MPPs manufactured by 3D printing have been reported. When introducing such new techniques, despite the conventional microdrill procedure, manufacturing accuracy can often become an issue. However, there are few studies reporting the effect of manufacturing accuracy on the acoustic properties in the case of 3D-printed MPPs. Considering this situation, in this pilot study, we attempted to produce MPPs with circular and rectangular perforations using a consumer 3D printer of the additive manufacturing type. The hole sizes of the specimens were measured, and the accuracy was evaluated. The normal incidence absorption coefficient and specific impedance were measured using an impedance tube. The measured results were compared with the theoretical values using Guo’s model. Through these basic studies, the MPPs produced by an additive manufacturing 3D printer demonstrated good sound absorption performance; however, due to the large deviations of parameters, the agreement with the theoretical values was not good, which suggests that it is difficult to predict the acoustic properties of MPPs made by a consumer-grade additive manufacturing 3D printer.

  MDPI AG, Aug. 2020, Acoustics, 2(3) (3), 605 - 616

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• A formulation of time-domain FEM for room acoustic simulations with frequency-dependent locally-reacting impedance boundary

  Takumi Yoshida, Takeshi Okuzono, Kimihiro Sakagami

  A room acoustic simulator using time-domain finite element method (TD-FEM) has been broadened its applicable range as a room acoustic design tool, recently. In the acoustic TD-FEM, constructing various sound absorber model is of crucial importance to perform reliable simulations. However, an accurate time-domain extended-reacting sound absorber model, which can take account for both frequency and incident angle dependence of sound absorption characteristics, has not been developed sufficiently due to the difficulties of modeling. The major difficulty is how to reflect frequency-dependent absorption characteristics efficiently in time-domain because its direct incorporation involves a convolution computation. In the present paper, a recently proposed auxiliary differential equations (ADE) method is applied to model the frequency-dependent locally-reacting impedance boundaries as a preliminary of constructing efficient extended-reacting model. The ADE method can reflect frequency-dependent behaviors in time-domain efficiently by solving additional first-order differential equations instead of the convolution computation. Numerical impedance tube problems demonstrate that the present TD-FEM can accurately simulate broadband absorption characteristics of various porous absorbers up to 10 kHz.

  Aug. 2020, Proceedings of Inter-Noise 2020, English

  [Refereed]

  International conference proceedings


• Experimental assessment of sound insulation performance of a double window with porous absorbent materials its cavity perimeter

  Yohei Tsukamoto, Yoshihiro Tomikawa, Kimihiro Sakagami, Takeshi OKuzono, Hidetoshi Maikawa, Yusuke Komoto

  As described herein, the sound insulation performance of a double window with absorbent materials on the perimeter of its cavity is studied experimentally. Two experiments are used to measure the sound reduction indices. The first experiment was performed with a double window composed of commercially available products. The second was conducted with a model constructed of two acrylic panels: a simplified model of a double window with a cavity between the panes. As the result of the first experiment, the improvement in reduction index obtained by the attached absorbent was around 4 dB. In the second experiment, though some negative effect was observed at low frequencies, the increase in reduction index was about 12 dB at maximum. Consequently, the following findings were obtained: (1) Acoustic transmission characteristics of a double window are affected mainly by resonances of two types: mass-air-mass resonance of window panes and the air cavity, and the acoustic mode resonances of the air cavity in-between; (2) acoustic mode resonance is suppressed by attaching absorbent materials on the inside of the cavity of window. Consequently, the sound reduction index increases.

  ELSEVIER, Aug. 2020, Applied Acoustics, 165, 107317, English, International magazine

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Locally implicit time-domain finite element method for sound field analysis including permeable membrane sound absorbers

  Takumi Yoshida, Takeshi Okuzono, Kimihiro Sakagami

  Acoustical Society of Japan, Jul. 2020, Acoustical Science and Technology, 41(4) (4), 689 - 692, English, International magazine

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Application of Paper Folding Technique to Three-Dimensional Space Sound Absorber with Permeable Membrane: Case Studies of Trial Productions

  Kimihiro Sakagami, Takeshi Okuzono, Hirotaka Suzuki, Nao Koyanagi, Masahiro Toyoda

  The authors propose a space sound absorber made of a permeable membrane (PM), including woven or non-woven fabrics in three-dimensional shapes, e.g., cylinder, rectangle, etc. The proposed absorbers are examined by experimental measurements and boundary element analyses, and it is found that they can be effectively used especially for middle and high frequencies. In order to develop these absorbers for wider applications, it would be desirable to give them additional values and functions, particularly to elaborate on their design. Supposing that they could also be used for lighting equipment, such as lampshades as one of the applications, pilot studies on pseudo-cylindrical, and pseudo-spherical PM space absorbers with uneven surfaces produced by paper-folding (origami technique) are carried out. The pseudo-cylindrical concave curves (PCCC) shell shape has been proven as a suitable form for a lampshade, and the pseudo-spherical concave curves (PSCC) shell shape is an application of PCCC. In this paper, PCCC and PSCC shell shapes are applied to three-dimensional PM space absorbers, and trials are conducted using PMs selected by flow resistance measurements and preliminary simulations. The sound absorptivity of the specimens is measured in a reverberation chamber, and their absorptivity is 0.6 (PCCC case) and 0.4 (PSCC case) at mid-high frequencies.

  INT INST ACOUSTICS & VIBRATION, Jun. 2020, INTERNATIONAL JOURNAL OF ACOUSTICS AND VIBRATION, 25(2) (2), 243 - 247, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Time Domain Room Acoustic Solver with Fourth-Order Explicit FEM Using Modified Time Integration

  Takumi Yoshida, Takeshi Okuzono, Kimihiro Sakagami

  This paper presents a proposal of a time domain room acoustic solver using novel fourth-order accurate explicit time domain finite element method (TD-FEM), with demonstration of its applicability for practical room acoustic problems. Although time domain wave acoustic methods have been extremely attractive in recent years as room acoustic design tools, a computationally efficient solver is demanded to reduce their overly large computational costs for practical applications. Earlier, the authors proposed an efficient room acoustic solver using explicit TD-FEM having fourth-order accuracy in both space and time using low-order discretization techniques. Nevertheless, this conventional method only achieves fourth-order accuracy in time when using only square or cubic elements. That achievement markedly impairs the benefits of FEM with geometrical flexibility. As described herein, that difficulty is solved by construction of a specially designed time-integration method for time discretization. The proposed method can use irregularly shaped elements while maintaining fourth-order accuracy in time without additional computational complexity compared to the conventional method. The dispersion and dissipation characteristics of the proposed method are examined respectively both theoretically and numerically. Moreover, the practicality of the method for solving room acoustic problems at kilohertz frequencies is presented via two numerical examples of acoustic simulations in a rectangular sound field including complex sound diffusers and in a complexly shaped concert hall.

  MDPI AG, May 2020, Applied Sciences, 10(11) (11), 3750 - 3750, English, International magazine

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Experimental comparison of absorption characteristics of single-leaf permeable membrane absorbers with different backing air cavity designs

  Takeshi Okuzono, Koji Uenishi, Kimihiro Sakagami

  Permeable membranes (PMs), which are air-permeable fabrics made from various natural or chemical fibers that are thinly woven or non-woven, are attractive sound-absorbing materials. The simplest PM absorber is a single-leaf PM absorber (PMSG) with a non-locally reacting rigid backed air cavity in which a PM is placed in front of a rigidly backed air cavity. A honeycomb-backed single-leaf PM absorber (PMHC), which has a locally reacting air cavity, is also well known. However, the two PM absorbers have shortcomings in their diffuse field absorption coefficients attrib- utable to the backing air cavity design. To overcome those shortcomings, we intro- duce a PM absorber array (PMAR): a single-leaf PM absorber with multiple locally reacting air cavities of different depths. As described herein, to present PMAR benefits, we experimentally compare the diffuse field absorption charac- teristics of the three single-leaf PM absorbers with different air cavity designs. Reverberation absorption coefficient measurements were taken using nine thin permeable membranes made of three chemical fibers, each having different flow resistance and surface density. Results show that PMAR is an effective sound ab- sorbing structure to overcome the shortcomings related to the diffuse field absorp- tion coefficients of PMSG and PMHC. Material property effects on permeable membranes are also demonstrated.

  Institute of Noise Control Engineering (INCE), May 2020, Noise Control Engineering Journal, 68(3) (3), 237 - 245, English, International magazine

  [Refereed]

  Scientific journal


• Potential of Room Acoustic Solver with Plane-Wave Enriched Finite Element Method

  Takeshi Okuzono, M Shadi Mohamed, Kimihiro Sakagami

  Predicting room acoustics using wave-based numerical methods has attracted great attention in recent years. Nevertheless, wave-based predictions are generally computationally expensive for room acoustics simulations because of the large dimensions of architectural spaces, the wide audible frequency ranges, the complex boundary conditions, and inherent error properties of numerical methods. Therefore, development of an efficient wave-based room acoustic solver with smaller computational resources is extremely important for practical applications. This paper describes a preliminary study aimed at that development. We discuss the potential of the Partition of Unity Finite Element Method (PUFEM) as a room acoustic solver through the examination with 2D real-scale room acoustic problems. Low-order finite elements enriched by plane waves propagating in various directions are used herein. We examine the PUFEM performance against a standard FEM via two-room acoustic problems in a single room and a coupled room, respectively, including frequency-dependent complex impedance boundaries of Helmholtz resonator type sound absorbers and porous sound absorbers. Results demonstrated that the PUFEM can predict wideband frequency responses accurately under a single coarse mesh with much fewer degrees of freedom than the standard FEM. The reduction reaches O(10^-2) at least, suggesting great potential of PUFEM for use as an efficient room acoustic solver.

  MDPI, Mar. 2020, Applied Sciences, 10(6) (6), 1969, English, International magazine, Co-authored internationally

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Implementation experiment of a honeycomb-backed MPP sound absorber in a meeting room

  HOSHI Kazuma, HANYU Toshiki, OKUZONO Takeshi, SAKAGAMI Kimihiro, YAIRI Motoki, HARADA Shinji, TAKAHASHI Seiji, UEDA Yasutaka

  This paper presents the absorption performance of honeycomb-backed micro perforated panel (MPP) absorbers, which are needed to improve the acoustics of an existing 91 m^3 small meeting room where the reverberation time is over two seconds from 250 Hz to 2 kHz, for comfortable speech communication. In Japan, MPPs are difficult to use combustible materials, particularly, panels with holes for interior walls owing to fire regulations. Therefore, we implemented the MPP absorber as an additional attachment that can be hung on walls and ceilings. First, the absorption characteristics of the MPP absorber were designed to reduce reverberation times at mid-frequency using an electroacoustical equivalent theory. Then, a wave-based finite element method simulation was used to determine the absorber placement. Absorption coefficients of the honeycomb-backed MPP absorber were also measured in an irregularly shaped reverberation chamber. Finally, the effect of the installed MPP absorbers was checked by acoustic parameter measurements. As a result, we observed that the reverberation time was reduced under 1.5 s in all frequencies, the equivalent absorption area doubled, the early decay time values were also reduced from 2.7 s to 1.0 s at 1 kHz, the clarity (C50,mid) increased by more than 5 dB, and the speech transmission index (STI) value increased from 0.55 to 0.67 by one rank up.

  Jan. 2020, Applied Acoustics, 157, 107000, English, International magazine

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Relationship between sound radiations resulting from airborne-sound and point-force excitations of a double-leaf infinite elastic plate

  YAIRI Motoki, SAKAGAMI Kimihiro, OKUZONO Takeshi

  Sep. 2019, Acoustical Science and Technology, 40(5) (5), 325 - 335, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• A locally implicit time-domain FEM for room acoustics simulation including permeable membrane absorbers

  YOSHIDA Takumi, OKUZONO Takeshi, SAKAGAMI Kimihiro

  Sep. 2019, Proceedings of 23rd International Congress on Acoustics, 763 - 770, English

  [Refereed]

  Scientific journal


• Dispersion-reduced time domain FEM for room acoustics simulation

  OKUZONO Takeshi, SAKAGAMI Kimihiro, OTSURU Toru

  This paper presents an overview of the applicability of implicit time-domain FEM (TD-FEM) for room acoustics simulation, which has fourth-order accuracy in both space and time. First, the TD-FEM algorithm is presented with explanations of dispersion-reduced finite elements for spatial discretization and a time integration method for time discretization. The theoretical dispersion error property is also shown. Use of the dispersion-reduced scheme presents benefits in terms of accuracy, stability and convergence of an iterative solver, which have a marked effect on the computational cost. Then, the applicability of TD-FEM is demonstrated using two numerical examples on room acoustics simulation in the kilohertz frequency range, which are acoustics simulations of a simply shaped concert hall and simulation of reverberation absorption coefficient measurements. In numerical examples of concert hall analysis, comparison with a conventional TD-FEM presents the efficiency of the dispersion-reduced TD-FEM. Modeling accuracy of non-locally reacting permeable membrane sound absorbers for the TD-FEM is presented through simulation of reverberation room method.

  Lead, Sep. 2019, Proceedings of 23rd International Congress on Acoustics, 6070 - 6077, English, International magazine

  [Refereed]

  International conference proceedings

  Link to Kobe Univ. Repository (Kernel)


• Predicting absorption characteristics of single-leaf permeable membrane absorbers using finite element method in a time domain

  Okuzono, T., Shimizu, N., Sakagami, K.

  Permeable membranes (PMs), which are air-permeable thin woven fabrics or non-woven fabrics, are attractive sound-absorbing materials used to control acoustics in buildings. Although the absorption characteristics of various PM absorbers have been studied extensively, it has not been established how to incorporate PMs into a wave-based acoustic simulation method known as the time-domain finite element method (TD-FEM). This paper presents a numerical model of limp PMs for TD-FEM as well as a computationally efficient TD-FEM for predicting sound fields including PMs. The limp PM model incorporates effects of both sound-induced vibration of PMs and the air permeability of PMs. Consequently, two mate- rial parameters are considered: the surface density and flow resistance of PMs. Verification of the limp PM model and efficiency evaluation of TD-FEM were first performed with an impedance tube problem. Then, reverberation absorption coefficients of single-leaf PM absorbers with a non-locally reacting rigid backed air cavity were predicted through simulation of a reverberation absorption coefficient measurement using the present TD-FEM at frequencies of 100 Hz to 2.5 kHz. The predicted results were compared with measured and theoretical values. To demonstrate the applicability of present TD-FEM, eight PMs, each with different flow resistance and surface density, were considered for comparison. Results revealed that the present TD-FEM with the limp PM model can predict the magnitude relation of absorption characteristics of single-leaf PM absorbers attributable to differences of material properties of PMs.

  Aug. 2019, Applied Acoustics, 151, 172 - 182, English, International magazine

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Note on microperforated panel model using equivalent-fluid-based absorption elements

  OKUZONO TAKESHI, NITTA TAKAO, SAKAGAMI KIMIHIRO

  May 2019, Acoustical Science and Technology, 40(3) (3), 221 - 224, English, International magazine

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Predicted Absorption Performance of Cylindrical and Rectangular Permeable Membrane Space Sound Absorbers Using the Three-Dimensional Boundary Element Method

  Masahiro Toyoda, Kota Funahashi, Takeshi Okuzono, Kimihiro Sakagami

  Three-dimensional, permeable membrane space sound absorbers have been proposed as practical and economical alternatives to three-dimensional, microperforated panel space sound absorbers. Previously, the sound absorption characteristics of a three-dimensional, permeable membrane space sound absorber were predicted using the two-dimensional boundary element method, but the prediction accuracy was impractical. Herein, a more accurate prediction method is proposed using the three-dimensional boundary element method. In the three-dimensional analysis, incident waves from the elevation angle direction and reflected waves from the floor are considered, using the mirror image. In addition, the dissipated energy ratio is calculated based on the sound absorption of a surface with a unit sound absorption power. To validate the three-dimensional numerical method, and to estimate the improvement in prediction accuracy, the results are compared with those of the measurements and two-dimensional analysis. For cylindrical and rectangular space sound absorbers, three-dimensional analysis provides a significantly improved prediction accuracy for any shape and membrane sample that is suitable for practical use.

  May 2019, Sustainability, 11(9) (9), 2714, English, International magazine

  [Refereed][Invited]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• A Basic Study on a Rectangular Plane Space Sound Absorber Using Permeable Membranes

  Takeshi Okuzono

  In this communication, the sound absorption characteristics of rectangular-shaped plane space sound absorbers without any backing structure using permeable membranes (PMs) are measured by reverberation room method. First, three types of PMs, in this study woven fabrics, are selected with different flow resistances and surface densities. They are prepared in the plane rectangular-shaped space absorbers of two different sizes. The measured results are discussed through comparison with the existing theoretical and measured results for absorbers of the other shapes or configurations. The present results and discussion demonstrate that the reverberation absorption coefficients of the proposed absorbers are low at low frequencies and converge to a moderately high value at high frequencies. Especially, ones with higher flow resistance than the air impedance converge to a value greater than 0.5, which is a theoretically estimated maximum absorption coefficient of infinite single-leaf PM. This is inferred to be attributed mainly to area effect. From these results the proposed absorbers can be used effectively despite of their very simple structure. Also it is found that the proposed absorber can offer higher sound absorption than permeable membrane absorbers of other shapes or configuration. Regarding the effect of the size, the absorbers of smaller size offer higher absorption coefficients regardless of material properties of the PMs used in the experiments.

  Apr. 2019, Sustainability, 11(7) (7), 2185, English, International magazine

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• A Pilot Study on the Sound Absorption Characteristics of Chicken Feathers as an Alternative Sustainable Acoustical Material

  Asniawaty Kusno, SAKAGAMI KIMIHIRO, OKUZONO TAKESHI, TOYODA MASAHIRO, OTSURU TORU, Rosady Mulyadi, Kusno Kamil

  Mar. 2019, Sustainability, 11(5) (5), 1476, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Basic study on relationship between airborne sound transmission and structure-borne sound radiation of a finite elastic plate

  Takahashi, Katsutoshi, Yairi, Motoki, Okuzono, Takeshi, Sakagami, Kimihiro, Toyoda, Masahiro

  Jan. 2019, Acoustical Science and Technology, 40(1) (1), 52 - 55, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Dispersion error reduction of absorption finite elements based on equivalent fluid model

  Okuzono, Takeshi, Sakagami, Kimihiro

  Sep. 2018, Acoustical Science and Technology, 39(5) (5), 362 - 365, English, International magazine

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• RELATIONSHIP BETWEEN SOUND RADIATION FROM SOUND-INDUCED AND FORCE-EXCITED VIBRATION

  YAIRI Motoki, SAKAGAMI Kimihiro, OKUZONO Takeshi

  Jul. 2018, Proc of 25th Internaltional Congress on Sound and Vibration, No.287, 1 - 8, English

  [Refereed][Invited]

  International conference proceedings


• IMPLEMENTATION EXPERIMENT OF A HONEYCOMB-BACKED MPP SOUND ABSORBING PANEL IN A MEETING ROOM

  HOSHI Kazuma, HANYUToshiki, SAKAGAMI Kimihiro, OKUZONO Takeshi, YAIRI Motoki, HARADA Shinji, TAKAHASHI Seiji, UEDA Yasutaka

  Jul. 2018, Proc of 25th Internaltional Congress on Sound and Vibration, No.1049, 1 - 8, English

  [Refereed][Invited]

  International conference proceedings


• A THREE-DIMENSIONAL TIME-DOMAIN FINITE ELEMENT METHOD BASED ON FIRST-ORDER ORDINARY DIFFERENTIAL EQUATIONS FOR TREATING PERMEABLE MEMBRANE ABSORBERS

  YOSHIDA Takumi, OKUZONO Takeshi, SAKAGAMI Kimihiro

  Jul. 2018, Proc of 25th Internaltional Congress on Sound and Vibration, No.838, 1 - 7, English

  [Refereed]

  International conference proceedings


• AN EXPERIMANTAL STUDY ON THE ABSORPTION CHARACTERISTICS OF PERMEABLE MEMBRANE ABSORBERS ARRAY

  OKUZONO Takeshi, UENISHI Koji, SAKAGAMI Kimihiro, SHIMIZU Hikaru

  Jul. 2018, Proc of 25th Internaltional Congress on Sound and Vibration, No.48, 1 - 6, English

  [Refereed][Invited]

  International conference proceedings


• Numerically stable explicit time-domain finite element method for room acoustics simulation using an equivalent impedance model

  Yoshida, Takumi, Okuzono, Takeshi, Sakagami, Kimihiro

  Corresponding, May 2018, Noise Control Engineering Journal, 66(3) (3), 176 - 189, English

  [Refereed]

  Scientific journal


• Relation between sound radiation from airborne-sound and point-force excitations of a double-leaf plate

  Motoki Yairi, Kimihiro Sakagami, Takeshi Okuzono

  An expanded theory for relating airborne-sound-excited and force-excited sound radiation from solid structures is presented. Although reduction of these two types of sound radiation is a fundamental issue in noise-control engineering, each of them has been treated as separate issues. A previous study established a fundamental relationship between the sound radiation from airborne-sound-excited and force-excited vibration of a single-leaf plate. A conversion function that relates the two excitation cases was presented in a simple closed-form, not including the plate’s parameters. In this paper, the applicability of the conversion function is expanded from a single-leaf infinite elastic plate model to a double-leaf plate model.

  Institute of Noise Control Engineering, 2018, INTER-NOISE 2018 - 47th International Congress and Exposition on Noise Control Engineering: Impact of Noise Control Engineering, English

  International conference proceedings


• A frequency domain finite element solver for acoustic simulations of 3D rooms with microperforated panel absorbers

  Takeshi Okuzono, Kimihiro Sakagami

  Microperforated panel (MPP) absorbers, which provide broadband sound absorption without the use of fibrous materials, have favorable material properties that support recyclability, flexibility of design, hygiene demands, and cleaning. Many earlier studies have specifically examined the development of absorbers themselves. However, to use the absorption performance of MPP absorbers sufficiently in room acoustic applications, it is beneficial to develop accurate prediction methods of sound fields in rooms with MPP absorbers. Such methods are expected to be useful for room acoustics design and absorber design tools. This study constructs a frequency domain finite element (FE) solver for acoustic simulations of a practical sized room with MPP absorbers. Then the accuracy and effectiveness are evaluated. In the FE solver, spatial domains are discretized by fourth-order accurate FEs in terms of dispersion error, and MPP absorbers are modeled using first-order hexahedral limp MPP elements that can deal with sound propagation in the backing structure of absorbers. First, the accuracy of present FE solver is demonstrated using impedance tube problems in comparison with conventional second-order accurate FEs. Results show higher convergence of solutions for the present FE solver. Then, exploration of an iterative solver for efficient multi-frequency analyses reveals that the recently developed CSQMOR is a faster and more stable solver. Finally, comparison with a conventional surface impedance model based on a locally reacting assumption confirms the effectiveness of present FE solver by presenting the importance of dealing with the incident angle dependence of reactance of a rigid-backed air cavity in the modeling of single leaf MPP absorbers. (C) 2017 Elsevier Ltd. All rights reserved.

  ELSEVIER SCI LTD, Jan. 2018, APPLIED ACOUSTICS, 129, 1 - 12, English, International magazine

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• A first-order ODE based explicit time-domain FEM for room acoustic simulations

  OKUZONO Takeshi, YOSHIDA Takumi, SAKAGAMI Kimihiro

  Aug. 2017, Proc of inter.noise2017, 371 - 379, English

  [Refereed][Invited]

  International conference proceedings


• An implicit time-domain finite element scheme for sound field analysis with permeable membrane absorbers

  OKUZONO Takeshi, SAKAGAMI Kimihiro, KATSUYAMA Akihiro

  Jul. 2017, Proc of 24th Internaltional Congress on Sound and Vibration, NO.961, 1 - 8, English

  [Refereed][Invited]

  International conference proceedings


• Chicken feather: An alternative of acoustical materials

  Asniawaty Kusno, Masahiro Toyoda, Kimihiro Sakagami, Takeshi Okuzono, Toru Otsuru, Kusno Kamil, Vovi Masgode

  Researchers' contributions on green materials development for sound insulation are increas-ingly in demand, including the abundant wasted chicken feathers. This study examines possi-bility of chicken feathers (CF) as an alternative acoustical material through understanding of its sound absorption characteristics. Common absorptive material glass wool (GW) applies as counterpart in measurements. Clean and dried CF is compacted in mesh prior to absorption coefficient measurement. Acoustical measurements by EA method were applied on typical thickness CF specimen of 48 and 60 kg/cm3 mesh densities. Specimen respond of absorption coefficient are relatively increase throughout frequency ranges of 100-1600 Hz, reaching maximum 0.99 at frequency 1600 Hz, 950 Hz, and 650 Hz for CF thickness 25, 50 and 75 mm, respectively. Measurement confirmation on glass wool (GW) specimen was resulted in comparable results. Flow resistivity test is applied for empirical model confirmation, resulted in diverged phenomenon and improperly fix to Miki's model as the common empirical model of fibrous acoustic materials. More measurements with variation on specimen densities should validate the possibility of chicken feathers as potential alternative of acoustical materials.

  International Institute of Acoustics and Vibration, IIAV, 2017, 24th International Congress on Sound and Vibration, ICSV 2017, English

  International conference proceedings


• Improved sound absorption performance of three-dimensional MPP space sound absorbers by filling with porous materials

  Masahiro Toyoda, Kimihiro Sakagami, Mitsuru Okano, Takeshi Okuzono, Emi Toyoda

  Because microperforated panels (MPPs), which can be made from various materials, provide wide-band sound absorption, they are recognized as one of the next-generation absorption materials. Although MPPs are typically placed in front of rigid walls, MPP space sound absorbers without a backing structure, including three-dimensional cylindrical MPP space absorbers (CMSAs) and rectangular MPP space absorbers (RMSAs), are proposed to extend their design flexibility and easy-to-use properties. On the other hand, improving the absorption performance by filling the back cavity of typical MPP absorbers with porous materials has been shown theoretically, and three-dimensional MPP space absorbers should display similar improvements. Herein the effects of porous materials inserted into the cavities of CMSA5 and RMSAs are experimentally investigated and a numerical prediction method using the two-dimensional boundary element method is proposed. Consequently, CMSA5 and RMSAs with improved absorption performances are illustrated based on the experimental results, and the applicability of the proposed prediction method as a design tool is confirmed by comparing the experimental and numerical results. (C) 2016 Elsevier Ltd. All rights reserved.

  ELSEVIER SCI LTD, Jan. 2017, APPLIED ACOUSTICS, 116, 311 - 316, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Finite element analysis of absorption characteristics of permeable membrane absorbers array

  Koji Uenishi, Takeshi Okuzono, Kimihiro Sakagami

  Corresponding, Acoustical Society of Japan, 2017, Acoustical Science and Technology, 38(6) (6), 322 - 325, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• 通気性膜を用いた立体型空間吸音体の吸音特性の3次元境界要素解析

  FUNAHASHI Kouta, TOYODA Masahiro, SAKAGAMI Kimihiro, OKUZONO Takeshi

  日本音響学会, Jul. 2016, 日本音響学会誌, 72(7) (7), 383 - 385, Japanese

  [Refereed]

  Scientific journal


• 長方形要素を用いた陽的時間領域有限要素法による室内音場解析のための修正積分則

  YOSHIDA Takumi, OKUZONO Takeshi, SAKAGAMI Kimihiro

  Corresponding, 日本音響学会, Jul. 2016, 日本音響学会誌, 72(7) (7), 367 - 373, Japanese

  [Refereed]

  Scientific journal


• Relationship between sound radiation from sound-induced and force-excited vibration: Analysis using an infinite elastic plate model

  Motoki Yairi, Kimihiro Sakagami, Kosuke Nishibara, Takeshi Okuzono

  Although sound radiation from sound-induced vibration and from force-excited vibration of solid structures are similar phenomena in terms of radiating from vibrating structures, the general relationship between them has not been explicitly studied to date. In particular, airborne sound transmission through walls and sound radiation from structurally vibrating surfaces in buildings are treated as different issues in architectural acoustics. In this paper, a fundamental relationship is elucidated through the use of a simple model. The transmission coefficient for random-incidence sound and the radiated sound power under point force excitation of an infinite elastic plate are both analyzed. Exact and approximate solutions are derived for the two problems, and the relationship between them is theoretically discussed. A conversion function that relates the transmission coefficient and radiated sound power is obtained in a simple closed form through the approximate solutions. The exact solutions are also related by the same conversion function. It is composed of the specific impedance and the wavenumber, and is independent of any elastic plate parameters. The sound radiation due to random-incidence sound and point force excitation are similar phenomena, and the only difference is the gradient of those characteristics with respect to the frequency. (C) 2016 Acoustical Society of America.

  ACOUSTICAL SOC AMER AMER INST PHYSICS, Jul. 2016, JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA, 140(1) (1), 453 - 460, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• An explicit time-domain finite element method for room acoustics simulations: Comparison of the performance with implicit methods

  Takeshi Okuzono, Takumi Yoshida, Kimihiro Sakagami, Toru Otsuru

  This paper presents the applicability of an explicit time-domain finite element method (TD-FEM) using a dispersion reduction technique called modified integration rules (MIR) on room acoustics simulations with a frequency-independent finite impedance boundary. First, a dispersion error analysis and a stability analysis are performed to derive the dispersion relation and the stability condition of the present explicit TD-FEM for three-dimensional room acoustics simulations with an infinite impedance boundary. Secondly, the accuracy and efficiency of the explicit TD-FEM are presented by comparing with implicit TD-FEM using MIR through room acoustics simulations in a rectangular room with infinite impedance boundaries. Thirdly, the stability condition of the explicit TD-FEM is investigated numerically in the case with finite impedance boundaries. Finally, the performance of the explicit TD-FEM in room acoustics simulations with finite impedance boundaries is demonstrated in a comparison with the implicit TD-FEM. Although the stability of the present explicit TD-FEM is dependent on the impedance values given at boundaries, the explicit TD-FEM is computationally more efficient than the implicit method from the perspective of computational time for acoustics simulations of a room with larger impedance values at boundaries. (c) 2015 Elsevier Ltd. All rights reserved.

  ELSEVIER SCI LTD, Mar. 2016, APPLIED ACOUSTICS, 104, 76 - 84, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• A note on the relationship between airborne sound transmission and structure-borne sound radiation: Basic study using classical approximate solution for a single-leaf elastic plate

  YAIRI MOTOKI, SAKAGAMI KIMIHIRO, OKUZONO TAKESHI, NISHIBARA KOSUKE

  日本音響学会, Feb. 2016, Journal of the Acoustical Society of Japan (J), 72(2) (2), 68 - 72, Japanese

  [Refereed]

  Scientific journal


• A time-domain finite element model of permeable membrane absorbers

  Takeshi Okuzono, Kimihiro Sakagami

  Acoustical Society of Japan, 2016, Acoustical Science and Technology, 37(1) (1), 46 - 49, English

  [Refereed]

  Scientific journal


• Acoustic absorption mapping: wide-area estimation of acoustic absorption coefficient using airborne hyperspectral imagery

  OSHIMA Takuya, WAKAMATSU Kei, HIRAGURI Yasuhiro, OKUZONO Takeshi, TOMIKU Reiji, OKAMOTO Noriko, OTSURU Toru

  © 2016, German Acoustical Society (DEGA). All rights reserved. Recent advances in outdoor acoustic propagation modeling and simulation techniques have enabled wide-area environmental noise assessment as represented by noise mapping. However, among main input information for such an assessment, ground acoustic properties are not available as a geographical dataset, whereas topography is readily obtainable as a digital surface model (DSM). In this paper, a wide-area estimation technique of ground acoustic absorption coefficient using remote sensing is explored. The selected sensor is a CASI-3 airborne hyperspectral imager, which provides high spectral and spatial resolutions in visible and near-infrared optical wavelengths. Hyperspectral images of 34 bands with a ground sampling distance of 1 m was acquired for a region of approximately 1570x3730 m2. Simultaneously, ground acoustic properties were measured using an in-situ technique at 8 locations in the imaged region, each of which has 36 measurement points. A modeling process using single and multiple regression analyses derived a set of equations that estimates the acoustic absorption coefficient from 160 to 3150Hz one-third-octave bands using the optical spectral reflectance tracked down to 3 bands. The acoustic absorption maps obtained by applying the derived model to the entire image provided qualitative validity of the model.

  2016, Proc of inter.noise2016, 1857 - 1864, English

  [Refereed]

  International conference proceedings


• Three-dimensional MPP and permeable membrane space sound absorbers: An overview

  SAKAGAMI KIMIHIRO, OKUZONO TAKESHI, YAIRI MOTOKI, TOYODA MASAHIRO

  WESPAC, Dec. 2015, Proceedings of 12th WESPAC, English

  [Refereed][Invited]

  International conference proceedings


• A comparison of absorption models of microperforated panel absorbers on room acoustics simulations using finite element method

  OKUZONO Takeshi, SAKAGAMI Kimihiro

  Dec. 2015, Proc of 12th Wespac, No.O4000037, 63 - 66, English

  [Refereed]

  International conference proceedings


• On the Relationship between the Normal Incidence Airborne Sound-excited and the Structurally-excited Sound Radiation from a Wall: A Theoretical Trial with Simplified Models

  Yairi, Motoki, Sakagami, Kimihiro, Nishibara, Kosuke, Okuzono, Takeshi

  Multi-Science Publishing, Oct. 2015, Building Acoustics, 22(2) (2), 109 - 122, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Distinct effects of moisture and air contents on acoustic properties of sandy soil

  Takuya Oshima, Yasuhiro Hiraguri, Takeshi Okuzono

  Knowledge of distinct effects of moisture content and air volume on acoustic properties of soil is sought to predict the influence of human activities such as cultivation on acoustic propagation outdoors. This work used an impedance tube with the two-thickness method to investigate such effects. For a constant moisture weight percentage, the magnitude of the characteristic impedance became smaller and the absorption coefficient became higher with increase of the air space ratio. For a constant air space ratio, the absorption coefficient became larger and the magnitude of the propagation constant became smaller with increasing moisture weight percentage. (C) 2015 Acoustical Society of America

  ACOUSTICAL SOC AMER AMER INST PHYSICS, Sep. 2015, JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA, 138(3) (3), EL258 - EL263, English

  [Refereed]

  Scientific journal


• A finite-element formulation for room acoustics simulation with microperforated panel sound absorbing structures: Verification with electro-acoustical equivalent circuit theory and wave theory

  Takeshi Okuzono, Kimihiro Sakagami

  A simple frequency-domain finite-element method (FD-FEM) for sound field analyses inside rooms installed with microperforated panel (MPP) sound absorbing structures is described here. This method can also analyze sound absorbing structures composed of MPPs and permeable membranes (PM) simply by changing the only material parameters of MPP into those of PM. As the first stage of the study, the validity of the present FD-FEM is tested through the numerical experiments based on the impedance tube method for measuring the absorption characteristics at normal incidence. In the numerical experiments, we calculated the absorption characteristics of a single MPP absorber, a double-leaf MPP space absorber and a space absorber composed of MPP and PM by using the FD-FEM in two-dimensions, and the computed absorption characteristics are compared with those calculated by an electro-acoustical equivalent circuit theory or a wave theory based on Helmholtz-Kirchhoff boundary integral equation. The results showed that the presented FD-FEM can analyze the absorption characteristics at normal incidence of the MPP sound absorbing structures accurately with the simplicity of the formulation. (C) 2015 Elsevier Ltd. All rights reserved.

  Corresponding, ELSEVIER SCI LTD, Aug. 2015, APPLIED ACOUSTICS, 95, 20 - 26, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• 通気性単一膜を用いた矩形平面状空間吸音体の残響室法吸音率測定

  SOMATOMO YU, OKUZONO TAKESHI, FUNAHASHI KOTA, SAKAGAMI KIMIHIRO, TOYODA MASAHIRO

  日本音響学会, Jun. 2015, 日本音響学会誌, 71(6) (6), 276 - 277, Japanese

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• An experimental study on the absorption characteristics of a three-dimensional permeable membrane space sound absorber

  Kimihiro Sakagami, Kota Funahashi, Yu Somatomo, Takeshi Okuzono, Chinami Nishikawa, Masahiro Toyoda

  In this study, we propose a rectangular and cylindrical three-dimensional space sound absorber using a permeable membrane and the absorption characteristics which are examined experimentally by reverberation room method. As a pilot study, a two-dimensional boundary element (2-D BEM) analysis is also conducted to predict the absorption characteristics of the absorbers. The experimental study revealed that the absorption coefficient is low at low frequencies and gradually increases with frequency. The absorption coefficient converges to 0.5 at the maximum which is similar to a single-leaf permeable membrane. The flow resistance and the surface density of the permeable membrane mainly affect the absorption characteristics at middle to high frequencies. At low frequencies, the heavy membrane contributes to the higher absorption performance. In the experiment specimens with high flow resistance produce higher absorptivity. Also, the cylindrical absorber shows slightly higher absorption coefficient than the rectangular absorber mainly at low frequencies. The 2-D BEM results show similar frequency characteristics as the measured values when the membrane's flow resistance and surface density are low, but the numerical values overestimate overall the absorptivity of the absorbers. (C) 2015 Institute of Noise Control Engineering.

  INST NOISE CONTROL ENGINEERING, May 2015, NOISE CONTROL ENGINEERING JOURNAL, 63(3) (3), 300 - 307, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Room acoustics simulation with single-leaf microperforated panel absorber using two-dimensional finite-element method

  Takeshi Okuzono, Kimihiro Sakagami

  The authors proposed a simple finite element (FE) formulation in order to predict sound fields in rooms with microperforated panel (MPP) absorbers, and its validity was also presented through comparisons with electro acoustical equivalent circuit theory and wave theory in numerical experiments based on an impedance tube method. A 2D room acoustics simulation with a single-leaf MPP absorber is performed, in which a surface impedance model based on a locally reactive assumption is also used for comparison. This model uses the normal-incidence normalized acoustic impedance on the surface of the MPP absorber under an impedance boundary condition based on the locally reactive assumption that neglects the incident-angle dependence of the normalized acoustic impedance. The results are compared with results obtained without the single-leaf MPP absorber in the 1/3-octave-band mean sound pressure level (SPL) and in the 1/3-octave-band SPL distribution. From the results, it is expected that the reduction effect of the SPL after installing the single-leaf MPP absorber will be overestimated overall when using the surface impedance model.

  Acoustical Society of Japan, 2015, Acoustical Science and Technology, 36(4) (4), 358 - 361, English

  [Refereed]

  Scientific journal


• Applicability of an explicit time-domain finite-element method on room acoustics simulation

  Takeshi Okuzono, Toru Otsuru, Kimihiro Sakagami

  The accuracy and efficiency of the explicit time-domain finite-element method (TD-FEM) was studied with the dissipation term on room acoustics simulation at high frequencies through a numerical comparison with the implicit TD-FEM for large-scale analysis. Sound fields inside the cubic cavity with finite impedance boundaries were computed to reveal the effect of the use of the backward difference in the dissipation term of the explicit method on the resulting accuracy in analysis at high frequencies. Computed sound pressures were compared with the reference solution obtained using the implicit method. In the computations, the time interval of the explicit method was again determined by the stability condition of the implicit method and was set to near the critical value. It can be said that this method is very useful for room acoustics simulation, in which the room shape can be approximated by cubic FEs. The applicability of the explicit method for more generalized cases using rectangular FEs and distorted FEs will be presented in the future, as well as derivations of dispersion relation and stability condition for three-dimensional analysis.

  Acoustical Society of Japan, 2015, Acoustical Science and Technology, 36(4) (4), 377 - 380, English

  [Refereed]

  Scientific journal


• A SIMPLE FREQUENCY DOMAIN FINITE-ELEMENT FORMULATION FOR PREDICTING ABSORPTION CHARACTERISTICS OF MICROPERFORATED PANEL ABSORBERS

  Takeshi Okuzono, Kimihiro Sakagami

  Sound-absorbing materials play an important role in the control of acoustics in built environments. Recently, the concept of sustainable acoustical materials is becoming important in the development of sound-absorbing materials. Microperforated panels (MPP) that can be made from any recyclable materials are one of such materials. Various MPP absorbers and prediction methods of their absorption characteristics have been proposed. Wave-based numerical methods such as the finite-element method (FEM) are one of the powerful tools to design MPP absorbers. In this paper, first, we present a simple and computationally-efficient frequency-domain FEM for predicting absorption characteristics of MPP absorbers, in which only two material parameters, MPP's acoustic impedance determined by Maa's theory and MPP's surface density, are used. Then, the effectiveness of the present FEM is tested through numerical experiments based on an impedance tube method for measuring sound absorption characteristics at normal incidence. In the numerical experiments, we calculated absorption characteristics of a single MPP absorber, a double-leaf MPP space absorber, and a space absorber composed of MPP and permeable membranes (PM), respectively, using the FEM. The results calculated using the FEM are verified by comparison with absorption characteristics calculated using electro-acoustical equivalent circuit theory and wave theory based on Helmholtz-Kirchhoff boundary integral equation. The numerical experiments revealed that the present FEM can be analyzed normal incidence sound absorption characteristics of MPP absorbers composed of MPP and PM, accurately, within the application range of the formulation.

  INT INST ACOUSTICS & VIBRATION, 2015, PROCEEDINGS OF THE 22ND INTERNATIONAL CONGRESS ON SOUND AND VIBRATION, 1 - 8, English

  [Refereed][Invited]

  International conference proceedings


• A basic study on the absorption characteristics of a three-dimensional permeable membrane space sound absorber

  K. Funahashi, Y. Somatomo, C. Nishikawa, K. Sakagami, T. Okuzono, M. Toyoda

  Due to limitations of computes, prediction of structure-borne sound remain difficult for large-scale problems. Herein a prediction method for low-frequency structure-borne sound transmissions on concrete structures using the finite-difference time-domain scheme is proposed. The target structure is modeled as a composition of multiple plate elements to reduce the dimensions of the simulated vibration field from three-dimensional discretization by solid elements to two-dimensional discretization. This scheme reduces both the calculation time and the amount of required memory. To validate the proposed method, the vibration characteristics using the numerical results of the proposed scheme are compared to those measured for a two-level concrete structure. Comparison of the measured and simulated results suggests that the proposed method can be used to simulate real-scale structures.

  The Japan Society of Mechanical Engineers, Dec. 2014, Journal of the Acoustical Society of America, 6, 18 - 21, English

  [Refereed]

  Scientific journal


• Finite element sound field analysis for correction of absorption coefficient in reverberation room

  TOMIKU Reiji, OTSURU Toru, OKAMOTO Noriko, OKUZONO Takeshi, AZECHI Yoshiki, YOSHIDA Tsuyoshi

  In this study, sound fields for the measurement of sound absorption coefficient by reverberation room method are analyzed by time domain finite element method. This study shows effectiveness of the analysis for investigation on causes of variation in the measurement results and improvement methods of the measurement. To evaluate an actual sound field for the measurement, the ratio of incident sound energy to the test material in those to all boundary of the measurement sound field is calculated from results of the finite element sound fields analysis. First, square sound pressure amplitudes of plane sound wave incident on absorption material are calculated in one-dimensional sound field. Next, the calculation method of the ratio of the measurement sound field is described. Finally, relationship among the ratio, shape of the measurement room, and characteristics of the test material is investigated, and it is shown that the bigger normal incident sound absorption coefficient of test material, the larger the change of the ratio for decay sound field regardless of room shape and surface area of test material.

  Nov. 2014, CD-ROM Proceedings of inter.noise 2014, English

  [Refereed]

  International conference proceedings


• Application of an in-situ measurement method using ensemble averaging technique to material development

  OKAMOTO Noriko, OTSURU Toru, TOMIKU Reiji, KAMIMIZU Takaaki, YAMAGUCHI Makoto, OKUZONO Takeshi

  Nov. 2014, CD-ROM Proceedings of inter.noise 2014, English

  [Refereed]

  International conference proceedings


• An explicit time-domain finite-element method for room acoustics simulation

  OKUZONO Takeshi, OTSURU Toru, SAKAGAMI Kimihiro

  Nov. 2014, CD-ROM Proceedings of inter.noise 2014, English

  [Refereed][Invited]

  International conference proceedings


• Absorption modeling with ensemble averaged impedance for wave-based room acoustics simulations

  OTSURU Toru, TOMIKU Reiji, OKUZONO Takeshi

  Nov. 2014, CD-ROM Proceedings of inter.noise 2014, English

  [Refereed]

  International conference proceedings


• A finite-element method using dispersion reduced spline elements for room acoustics simulation

  Takeshi Okuzono, Toru Otsuru, Reiji Tomiku, Noriko Okamoto

  This paper presents a finite element method (FEM) using hexahedral 27-node spline acoustic elements (Sp127) with low numerical dispersion for room acoustics simulation in both the frequency and time domains, especially at higher frequencies. Dispersion error analysis in one dimension is performed to increase the accuracy of FEM using Sp127 by modifying the numerical integration points of element stiffness and mass matrices. The basic accuracy and efficiency of the FEM using the improved Sp127, which uses modified integration points, are presented through numerical experiments using benchmark problems in both the frequency and time domains, revealing that FEM using the improved Sp127 in both domains provides more accurate results than the conventional method does, and with fewer degrees of freedom. Moreover, the effectiveness of FEM using the improved Sp127 over that using hexahedral 27-node Lagrange elements is shown for time domain analysis of the sound field in a practical sized room. (C) 2013 Elsevier Ltd. All rights reserved.

  ELSEVIER SCI LTD, May 2014, APPLIED ACOUSTICS, 79, 1 - 8, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• 通気性膜を用いた立体型空間吸音体の吸音特性に関する基礎的研究

  FUNAHASHI Kota, SOMATOMO Yu, NISHIKAWA Chinami, SAKAGAMI Kimihiro, OKUZONO Takeshi, TOYODA Masahiro

  神戸大学大学院工学研究科, 2014, 神戸大学大学院工学研究科・システム情報学研究科紀要, 6(6) (6), 17 - 23, Japanese

  [Refereed]

  Research institution

  Link to Kobe Univ. Repository (Kernel)


• Finite element method

  Toru Otsuru, Takeshi Okuzono, Noriko Okamoto, Yusuke Naka

  Finite element method (FEM) is widely used in various engineering fields to solve problems with too many complexities to be dealt with by certain conventional approaches. In 1943, Courant proposed the theoretical basis of the method, and, in 1956, Turner et al. published both fundamental theory and application of FEM, namely "Stiffness deflection analysis", to solve structural problems [1, 2]. A decade and several years latter, FEM has been come to be applied to solve various acoustic problems [3-5]. Compared with other numerical techniques, FEM is advantageous in its broad range of applicability. However, FEM requires discretization of the domain, which results in huge amount of degrees-of-freedom especially when a three-dimensional domain is analyzed. Nevertheless, the matrices constructed in a standard FEM procedure have rather simple mathematical structures with sparseness. The simplicity makes their computationmore efficient especially when they are processed on a parallel/vector processors. Generally speaking, the iterative methods are suitable for solving such a sparse matrix equation efficiently with far lessmemory space on a computer. In this chapter, fundamentals, improvements, and applications of FEM on acoustic problems are explored.

  Springer Japan, Nov. 2013, Computational Simulation in Architectural and Environmental Acoustics: Methods and Applications of Wave-Based Computation, 9784431544548, 53 - 78, English

  [Refereed]

  In book


• Dispersion-reduced spline acoustic finite elements for frequency-domain analysis

  Takeshi Okuzono, Toru Otsuru, Reiji Tomiku, Noriko Okamoto

  A study was conducted to demonstrate the use of dispersion-reduced spline (Spl27) acoustic finite elements for frequency-domain analysis. It was demonstrated that Spl27 used the natural cubic spline polynomial of degree 3 to construct the shape function. The shape function in three dimensions for Spl27 was defined by using the natural cubic spline polynomial. The resulting dispersion relation was used to design an improved Spl27 with low dispersion. A finite-element mesh consisting of three-node spline line elements of nodal distance d was also considered to conduct the investigations. The proposed method modified the numerical integration points of element stiffness matrix and mass matrix, while the integration points were calculated from a condition that minimizes the dispersion error at an arbitrary non-dimensional wave number on an one-dimensional mesh.

  2013, Acoustical Science and Technology, 34(3) (3), 221 - 224, English

  [Refereed]

  Scientific journal


• A practical system to predict the absorption coefficient, dimension and reverberation time of room using GLCM, DVP and neural network

  M. N. Yahya, T. Otsuru, R. Tomiku, T. Okuzono

  Various prediction techniques of reverberation time such as the Sabine and Eyring equations, ray-method, and numerical method require main parameters such as the absorption coefficient and dimensions. Normally, these parameters are obtained from references or/and measurements that necessitate special equipment and skills. On that matter, the authors have proposed a new practical technique to identify the absorption coefficient and dimensions of rooms. The technique comprises Subsystem_1 and Subsystem_2, each of which uses photographic images. Subsystem_1 uses a Gray Level Co-occurrence Matrix (GLCM) and is integrated with a Neural Network (NN) to identify the absorption coefficient of the material. Subsystem_2 uses a Dimension Vision Predictor (DVP) with the author's "ruler method" to identify the dimensions. Examinations conducted in practical rooms revealed a good correlation coefficient of r ≥ 0.90 for Subsystem_1 and r ≥ 0.99 for Subsystem_2. Finally, the System using NN gave inconsistent results, while FEA revealed consistent results with r ≥0.8. © Universiti Malaysia Pahang.

  Universiti Malaysia Pahang, 2013, International Journal of Automotive and Mechanical Engineering, 8(1) (1), 1256 - 1266, English

  [Refereed]

  Scientific journal


• Relationship between dispersion error and accuracy of room acoustics parameter in time-domain finite-element room acoustics simulation

  OKUZONO Takeshi, OTSURU Toru, TOMIKU Reiji, OKAMOTO Noriko

  The time-domain finite-element method (TD-FEM) is a powerful wave-based numerical method for room acoustics simulation. However, it is well known that this method incurs an inherent error, called dispersion error, due to both spatial and time discretizations. To obtain a reliable result, discretization of both space and time, which maintain the dispersion error within acceptable level, is required, although the level for room acoustics applications such as calculating of the room acoustical parameters still remains unclear. Further, sufficiently fine spatial and time discretizations for reducing the error make the computation expensive. For efficient use of the method in practical applications, the balance between accuracy and computational cost needs to be considered. For the purpose, this paper presents the relationships between the dispersion errors and accuracy of room acoustical parameters in TD-FE analysis with fourth-order accuracy. Five room acoustical parameters of a sound field in a rectangular room with volume of 62 m3 were computed at frequencies from 250 Hz to 1 kHz, using TD-FEM with FE meshes of different spatial resolutions and with different time resolutions. Also, the dispersion errors in each analysis were theoretically estimated by dispersion error analysis in three dimensions. Results showed that the use of FE meshes having dispersion error below 0.52 % is recommended to yield the reasonable results at given frequency range.

  2013, CD-ROM Proceedings of Inter-Noise 2013, 2, 1300 - 1307, English

  [Refereed]

  International conference proceedings


• Humidity effect on pressure-velocity sensor examined in sound absorption measurement with ensemble averaging technique

  OTSURU Toru, KUSNO Asniawaty, TOMIKU Reiji, OKUZONO Takeshi, OKAMOTO Noriko, NAZLI Bin Che Din

  2013, CD-ROM Proceedings of Inter-Noise 2013, English

  [Refereed]

  International conference proceedings


• Application of modified integration rule to time-domain finite-element acoustic simulation of rooms

  Takeshi Okuzono, Toru Otsuru, Reiji Tomiku, Noriko Okamoto

  The applicability of the modified integration rule for time-domain finite-element analysis is tested in sound field analysis of rooms involving rectangular elements, distorted elements, and finite impedance boundary conditions. Dispersion error analysis in three dimensions is conducted to evaluate the dispersion error in time-domain finite-element analysis using eight-node hexahedral elements. The results of analysis confirmed that fourth-order accuracy with respect to dispersion error is obtainable using the Fox-Goodwin method (FG) with a modified integration rule, even for rectangular elements. The stability condition in three-dimensional analysis using the modified integration rule is also presented. Numerical experiments demonstrate that FG with a modified integration rule performs much better than FG with the conventional integration rule for problems with rectangular elements, distorted elements, and with finite impedance boundary conditions. Further, as another advantage, numerical results revealed that the use of modified integration rule engenders faster convergence of the iterative solver than a conventional rule for problems with the same degrees of freedom. (C) 2012 Acoustical Society of America. [http://dx.doi.org/10.1121/1.4730920]

  ACOUSTICAL SOC AMER AMER INST PHYSICS, Aug. 2012, JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA, 132(2) (2), 804 - 813, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Large-scale finite element sound field analysis of rooms using a practical boundary modeling technique

  Tom Otsuru, Takeshi Okuzono, Reiji Tomiku, Kusno Asniawaty, Noriko Okamoto

  Various kinds of computational methods based on the wave acoustics to analyze sound fields of rooms have been developed and used widely in these days. The authors have developed large-scale finite element sound field analysis (LsFE-SFA) in both frequency and time domains to analyze the sound field in practical rooms with complicated boundary conditions. Although LsFE-SFA can deal with discretized systems with some millions of degrees of freedom, some technique for modeling the absorption of the boundaries is required. Then, to provide practical and effective boundary conditions for computational methods on room acoustics, the authors have proposed ensemble averaged surface normal impedance including the fundamental measurement technique. In this paper, a brief summary of LsFE-SFA is given and a short explanation of newly developed acoustic element based on the modified integral rule is described. Next, the concept of the ensemble averaged surface normal impedance is explained. Finally, several application analyses of rooms are conducted to show the appllicability and capability of the techniques.

  2012, 19th International Congress on Sound and Vibration 2012, ICSV 2012, 1, 33 - 40, English

  International conference proceedings


• Practical subsystems to identify room dimensions and material surfaces using photograph images for room acoustic simulations

  Musli Nizam Bin Yahya, Toru Otsuru, Reiji Tomiku, Takeshi Okuzono, Toshiki Nagasawa, Tomohiro Oda

  A practical technique for simulating room acoustics parameters is proposed. The technique comprises Subsystems 1 and 2, each of which uses photographic images. Subsystem 1 uses a Gray Level Cooccurrence Matrix and a Feed Forward Neural Network to identify material surfaces. Subsystem 2 uses a Dimension Vision Predictor with the author's "ruler method" to identify the dimensions. Examinations conducted in practical rooms revealed good correlation coefficients of r ≥ 0.90 for Subsystem 1 and r ≥ 0.99 for Subsystem 2. Finally, simulations of reverberation times were conducted using Finite Element Analysis (FEA) with identified parameters. Sufficient agreement was confirmed.

  2012, AIJ Journal of Technology and Design, 18(39) (39), 601 - 606, English

  [Refereed]

  Scientific journal


• Applications of finite element sound field analysis using ensemble averaged surface normal impedance measured in-situ

  Toru Otsuru, Reiji Tomiku, Noriko Okamoto, Takeshi Okuzono, Kusno Asniawaty, Chihiro Ueki, Nazli Bin Che Din

  To analyze the sound fields in practical rooms with complex boundaries, the authors have developed the large-scale finite element sound field analysis in both frequency and time domains. Although the surface normal impedances of boundaries are required in the modeling process of a room's boundary conditions, not enough amounts of the impedances are available. Then, to provide practical boundary conditions for numerical simulations, the authors have also presented the concept and theoretical background of ensemble averaged surface normal impedance including the measurement method. Herein, brief summaries of the the concept of the ensemble averaged surface normal impedance and the finite element sound field analysis are given firstly. Next, the outline and the results of several impedance measurements using the method conducted in a seminar room are shown and the stabilities of the results are confirmed. Then, a post-processing technique using low-pass-filter and Akaike's information criteria is performed to make the measured impedance into more suitable form for numerical applications. Finally, several application analyses of rooms' sound fields are conducted to show the resulting accuracy of the finite element sound field analysis with the post-processed impedances. Copyright © (2011) by the Institute of Noise Control Engineering.

  2011, 40th International Congress and Exposition on Noise Control Engineering 2011, INTER-NOISE 2011, 2, 1462 - 1467, English

  International conference proceedings


• Development of practical System for prediction the absorption coefficients, dimensions and reverberation time of classroom using photo image and feed-forward neural network

  Musli Nizam Bin Yahya, Toru Otsuru, Reiji Tomiku, Takeshi Okuzono

  A prediction technique using photo image and feed forward neural network (FFNN) is proposed. Absorption coefficient and dimension are the main parameters for predicting a room's acoustic indices e.g. reverberation time (RT). Therefore, this study develops two simple Sub-systems to predict those parameters. Sub-system-1 uses Gray level co-concurrence matrix (GLCM) and FFNN to predict the absorption coefficient, whereas, Sub-system-2 uses VDP (Vision Dimension Predictor) with the author's "ruler method" to predict dimensions of the room. Predicted results from both the sub-systems are used in a System (using FFNN) and also in a finite element analysis (FEA) to predict the RT. We examined the reliability in four actual rooms and found that a high correlation coefficient r ≥ 0.9 was obtained for Sub-system-1. While, high correlation coefficient r ≥ 0.99 was obtained for Sub-system-2. Furthermore, System using FFNN gave inconsistent results (r = 0.23). However, FEA indicated consistent results with good correlation coefficient r ≥ 0.85.

  2011, 40th International Congress and Exposition on Noise Control Engineering 2011, INTER-NOISE 2011, 4, 2928 - 2933, English

  International conference proceedings


• Finite element sound field analysis in a reverberation room using ensemble averaged surface normal impedance

  Reiji Tomiku, Toru Otsuru, Noriko Okamoto, Takeshi Okuzono, Takahiro Shibata

  The purpose of this paper is to indicate the effectiveness of an ensemble averaged surface normal impedance, which are measured by the authors' proposed method: EA method, as an boundary condition of the sound field analysis by wave-based numerical methods. Firstly, sound fields in an irregularly shaped reverberation room with glass wool located on floor are analyzed by time domain finite element method (TDFEM). In those analyses, two types of surface normal impedance, i.e. the ensemble averaged surface normal impedance at random incidence and surface normal impedance at normal incidence, are considered as a boundary condition of the glass wool. Then, impulse responses and decay curves of the sound field obtained by the TDFEM are compared with those obtained by the measurements. The results using the ensemble averaged surface normal impedance show better agreement with measured values than those using the surface normal impedance at normal incidence. Copyright © (2011) by the Institute of Noise Control Engineering.

  2011, 40th International Congress and Exposition on Noise Control Engineering 2011, INTER-NOISE 2011, 2, 1475 - 1480

  International conference proceedings


• Fundamental accuracy of time domain finite element method for sound-field analysis of rooms

  Takeshi Okuzono, Toru Otsuru, Reiji Tomiku, Noriko Okamoto

  This paper presents an assessment of the accuracy and applicability of a time domain finite element method (TDFEM) for sound-field analysis in architectural space. This TDFEM incorporates several techniques: (1) a hexahedral 27-node isoparametric acoustic element using a spline function; (2) a lumped acoustic dissipation matrix; and (3) Newmark time integration method with an absolute diagonal scaled COCG iterative solver. Sound fields in an irregularly shaped reverberation room of 166 m(3) are computed using TDFEM. The computed values and measured values for 125-500 Hz are compared, revealing that the fine structure of the computed band-limited impulse responses agree with measured ones up to 0.1 s, with a cross-correlation coefficient greater than 0.93. The cross-correlation coefficient decreases gradually over time, and more rapidly for higher frequencies. Moreover, the computed decay curves, and the reverberation times, agree well with the respective measured ones, and with a better fit the higher the frequency (up to 500 Hz). (C) 2010 Elsevier Ltd. All rights reserved.

  ELSEVIER SCI LTD, Oct. 2010, APPLIED ACOUSTICS, 71(10) (10), 940 - 946, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Basic investigation on boundary shape modeling for sound field analysis of rooms using time domain finite element method

  Takeshi Okuzono, Toru Otsuru, Reiji Tomiku, Noriko Okamoto, Naoya Kitamura

  With the rapid progress of computer technology, numerical simulations based on the wave equation such as FEM and BEM have come to be powerful tools for acoustical design process. The authors have been developing a system of large scale finite element sound field analysis in both time and frequency domains in order to analyze sound fields in rooms with complicated boundary conditions. One of the problems to use the numerical simulations for design process is how to model the complicated geometries of architectural spaces. Typically, architectural spaces have several uneven structures like window, door and light fixture and so on. Although it is possible to model geometry of the structures including small details such as a window frame, a simulation using FE model with detailed room geometry requires a large computational cost. From a practical point of view, therefore, the use of simplified FE model that does not affect acoustics of rooms is desired. In this paper, a series of simulations using FE model with different approximation level of room geometry are conducted to reveal the influence of the use of FE models with different geometry representations on the simulated sound field of rooms. A small office with the volume of 55 m 3 is selected for the simulation and four FE model are created. The impulse responses and several room acoustical parameters such as T 30, EDT and D 50 obtained from each simulation are compared at frequencies of 125-1k Hz. Copyright © (2010) by the International Congress on Acoustics.

  2010, 20th International Congress on Acoustics 2010, ICA 2010 - Incorporating Proceedings of the 2010 Annual Conference of the Australian Acoustical Society, 2, 1529 - 1533, English

  International conference proceedings


• Ensamble averaged surface normal impedance measured in-situ; A trial application onto finite element sound field analysis

  Toru Otsuru, Reiji Tomiku, Noriko Okamoto, Takeshi Okuzono, Kusno Asniawaty, Nazli Che Din, Chihiro Ueki

  In the authors' former papers, we presented the concept and theoretical background of ensemble averaged surface normal impedance. The purpose of this paper is to show an application of the measurement method onto a realistic room and to present its plausibility when the measured impedances are supplied as boundary conditions of the finite element sound field analysis. The absorbent building-components in the room are classified into porous-, reflective-, and plate-vibration- types, and measured impedances of the three types show their tendencies properly. Finally, band-pass-filtered impulse responses are computed by using the FE-analysis using the measured impedances and the computed results agreed well with measured values using time stretched pulse method in the room.

  2010, 39th International Congress on Noise Control Engineering 2010, INTER-NOISE 2010, 6, 4264 - 4273, English

  International conference proceedings


• Accuracy and efficiency of time domain finite element method for sound field analysis of rooms

  Takeshi Okuzono, Toru Otsuru, Reiji Tomiku, Noriko Okamoto

  Various numerical methods based on the wave equation have been developed and utilized in many fields on acoustics. Due to high computational cost, it is still not easy for a method like the finite element method (FEM) to compute a room impulse response up to high frequency region if the room has rather a big volume like a music hall. To efficiently predict the sound field, the authors have been developing a system of large-scale finite element sound field analysis (LsFE-SFA) both in the time and the frequency domains. In this paper, accuracy and efficiency of a time domain FEM (TDFEM) are investigated. Sound pressure waveforms in a cubic room with the volume of 64 m3 are computed both by the TDFEM and time domain finite difference method (TDFDM), and the results are compared to reveal the effects of both spatial and time resolutions. The results show that TDFEM requires less computational cost than that of TDFDM. Next, frequency response in an office room with the volume of 70 m3 is computed by TDFEM and frequency domain FEM (FDFEM), and the results show that the agreement between the two methods is excellent. Moreover, calculation of frequency response by the TDFEM is effective when slow convergence of iterative method applied on FDFEM is preliminarily expected for a given sound field.

  2009, 38th International Congress and Exposition on Noise Control Engineering 2009, INTER-NOISE 2009, 6, 4344 - 4352

  International conference proceedings


• Sound field analysis of rooms by time domain finite element method with an iterative method

  Takeshi Okuzono, Toru Otsuru, Noriko Okamoto, Reiji Tomiku

  An iterative method is applied to time domain finite element method (TDFEM) to reduce the computational cost. First, eigenvalues distributions of coefficient matrix A] of linear systems [A]{x} = {b} arise in TDFEM are calculated to reveal the matrix property for basic sound field analysis. Then, convergence behaviors of preconditioned COCG method are shown for practical sound field analyses. Results show that [A] of [A]{x} = {b} arise in TDFEM has good property, which leads fast convergence of preconditioned COCG method, and the method converges with about 20 iterations per time step regardless of sound field and degrees of freedom if convergence criterion be set to 10-6.

  Jun. 2008, Journal of Environmental Engineering, 73(628) (628), 701 - 706, Japanese

  [Refereed]

  Scientific journal


• 有限要素法による室内音場解析に関する研究 : 大規模多目的ホール内部音場の試行的解析

  岡本 則子, 大鶴 徹, 奥園 健

  九州大学情報基盤センター, Mar. 2007, 九州大学情報基盤センター広報 : 全国共同利用版, 6(3) (3), 182 - 184, Japanese


• 有限要素法による室内音場の時間応答解析に関する研究

  奥園 健, 大鶴 徹, 岡本 則子

  九州大学情報基盤センター, Mar. 2007, 九州大学情報基盤センター広報 : 全国共同利用版, 6(3) (3), 185 - 187, Japanese


• Time domain large-scale finite element sound field analysis of a multi-purpose hall

  Toru Otsuru, Takeshi Okuzono, Noriko Okamoto, Kota Isobe, Hiroshi Furuya

  The authors have been developing Large-scale Finite Element Sound Field Analysis, or LsFE-SFA for short, to analyze sound fields in architectural rooms with complicated boundary conditions. The main purpose of this paper is to show its applicability and accuracy when a realistic large-scale sound field is to be analyzed in the time domain. A multi-purpose hall (A-hall, for short) with the volume of more than 37, 000 m3 and about 2, 500 seats is analyzed hereafter. At first, both mathematical basis of time domain LsFE-SFA is explained briefly. Then, both frequency and time domain LsFE-SFA were applied onto the sound field in A-hall. In the analyses, two types of boundary modeling, with or without balcony, were given into the computations. The values of absorption coefficient of materials except auditorium side-walls were given by referring literatures, and that of side-walls were given by in-situ measurement following some of the authors' EA-Noise method. By the frequency domain LsFE-SFA, sound pressure level distribution contour maps at 63 and 125 Hz were computed and the results were confirmed to be good. Then, the 1/3 octave band filtered impulse responses centered at 63 Hz and 125 Hz were computed by the time domain LsFE-SFA, and fair agreements with measured data were found. Finally, the results by the time domain LsFE-SFA were transformed into the frequency domain and the relative sound pressure level distributions of them showed excellent agreement with those computed by the frequency domain LsFE-SFA directly.

  2007, 14th International Congress on Sound and Vibration 2007, ICSV 2007, 3, 2442 - 2449, English

  International conference proceedings


• Time domain finite element sound field analysis of rooms using iterative methods and parallelization

  Takeshi Okuzono, Toshihide Sueyoshi, Toru Otsuru, Noriko Okamoto, Reiji Tomiku

  Generally, when a three-dimensional sound field is to be analyzed by a numerical method, the memory requirement to store the discretized variables tends to become enormous especially when the scale of the sound field is relatively large. While, iterative methods are used widely to solve linear equations on large-scale problems of many physical phenomena, and the methods are also effectively installed onto parallel computers with some parallelization techniques. Here, three iterative methods and a parallelization technique are applied onto finite element sound field analysis of rooms in time domain, and the performances of them are examined. First, the convergences of the methods, i.e. COCG, CGS and BiCGStab, are compared. All the methods converge at every time steps in the analysis of a cubic cavity, and COCG method is found to be the most efficient. Results obtained by COCG method are compared with those of the direct method to show excellent agreement if convergence criteria be set to 10 -6. Finally, the effect of parallelization by OpenMP applied onto a sound field analysis of a regularly shaped reverberation room are examined to result the speedup by 3.6 at 4 processors on a shared memory multiprocessor system.

  2006, Institute of Noise Control Engineering of the USA - 35th International Congress and Exposition on Noise Control Engineering, INTER-NOISE 2006, 3, 1909 - 1916, English

  International conference proceedings


• Impedance measurement of materials by use of ambient noise for computational acoustics

  Toru Otsuru, Takeshi Okuzono, Noriko Okamoto, Reiji Tomiku, Yasuo Takahashi

  Although various kinds of computational methods have been developed and utilized in many fields on acoustics, there exists only an insufficient amount of database of normal impedance of boundary materials. To overcome the situation, some of the authors proposed an efficient method in former papers that uses two-microphones, pp-sensor, and ambient noise to measure normal impedance of materials in-situ.The purpose of this paper is to give a further validity of the method that utilizes ambient noise by comparing the results obtained by the method with pp-sensor and by one with pu-sensor, or particle-velocity sensor "Microflown" combined with a miniature microphone. First, the basic characteristics of the pu-sensor were measured, and the validity of the particle velocity measured by the pu sensors with the authors' calibration procedure were confirmed in the frequency ranging from 100 Hz to 1500 Hz. Second, absorption coefficients of a glass wool measured by the method with both sensors in a reverberation room were compared. Finally, an example finite element computation of a sound field in a reverberation room by help of the measured impedance values was carried out to give satisfactory agreements.

  2006, Institute of Noise Control Engineering of the USA - 35th International Congress and Exposition on Noise Control Engineering, INTER-NOISE 2006, 8, 5261 - 5268, English

  International conference proceedings


• Accuracy of large-scale finite element sound field analysis in rooms by use of a Benchmark Platform

  Noriko Okamoto, Reiji Tomiku, Toru Otsuru, Takeshi Okuzono, Yosuke Yasuda

  In former papers, the authors have proposed the large-scale finite element sound field analysis (LsFE-SFA). However, the accuracy of the LsFE-SFA for a large-scaled room such as a concert hall has not been validated yet. In this paper, the accuracy is investigated by comparing the results obtained by LsFE-SFA with those by fast multipole BEM (FMBEM), which is an efficient BEM based on the fast multipole algorithm. In the investigation, the benchmark problems listed on the website were utilized, and the website is" Benchmark Platform on Computational Methods for Architectural/Environmental Acoustics, "which have been provided by Architectural Institute of Japan. First of all, the sound field in an irregularly shaped reverberation room was analyzed both by LsFE-SFA and by FMBEM, and the sound pressure distribution was measured to compare. The mean residuals of the sound pressure levels computed both by LsFE-SFA and by FMBEM to the measured values were less than 1.0 dB respectively. Finally, sound fields of a small hall were computed by both methods and the agreement of the results was found to be excellent, and the computation time and the required memory of the computations are given for further reference.

  2006, Institute of Noise Control Engineering of the USA - 35th International Congress and Exposition on Noise Control Engineering, INTER-NOISE 2006, 3, 1902 - 1908, English

  International conference proceedings

• 音響数値シミュレーションのシーズ

  奥園健, 吉田卓彌, 阪上公博

  Lead, Mar. 2022, 第81回音シンポジウム資料 建築音響測定への数値シミュレーションの活用とその可能性, 49 - 56, Japanese

  Lecture materials


• Simulating room acoustics with plane-wave-enriched finite element method

  Takeshi Okuzono

  Lead, Feb. 2022, 日本音響学会誌, 78(2) (2), 73 - 80, Japanese, Domestic magazine

  Introduction scientific journal


• Implementation experiment of a honeycomb-backed MPP sound absorbing system in a meeting room

  SAKAGAMI KIMIHIRO, 矢入 幹記, 奥園 健, 羽入 敏樹, 星 和磨, 原田 慎史, 高橋 誠治, 上田 泰孝

  日本音響材料協会, Jun. 2017, Architectural acoustics and noise control, 46(178) (178), 58 - 62, Japanese

  Report scientific journal

  Link to Kobe Univ. Repository (Kernel)


• 有限要素法による実在建築空間の音場予測

  奥園健, 大鶴徹, 富来礼次, 岡本則子, 巳之口俊史

  Lead, 九州大学情報統括本部広報委員会, Oct. 2009, 九州大学情報基盤研究開発センター全国共同利用システム広報, 3(1) (1), 24 - 27, Japanese

  Introduction research institution

• 音環境の数値シミュレーションー波動音響解析の技法と応用ー［第二版］

  Contributor, 第3章、第8章8.1を担当, 日本建築学会, Dec. 2021, Japanese, ISBN: 9784818926714

  [Refereed]


• Computational Simulation in Architectural and Environmental Acoustics-Methods and Applications of Wave-Based Computation-

  OKUZONO Takeshi, ASAKURA Takumi, HORINOUCHI Yoshinari, HOSHI Kazuma, INOUE Naohisa, ISHIZUKA Takashi, KAWAI Yasuhito, MASUMOTO Takayuki, NAKA Yusuke, OKAMOTO Noriko, OKUBO Kan, OKUBO Tomonao, ONITSUKA Hirofumi, OSHIMA Takuya, OTSURU Toru, SAKAMOTO Shinichi, SAKUMA Tetsuya, SUZUKI Hisaharu, TOMIKU Reiji, TOYODA Masahiro, TSURU Hideo, YASUDA Yosuke, YOKOTA Takatoshi

  Joint work, Springer, Aug. 2014, English, ISBN: 9784431544531

  Scholarly book


• Computational Simulation of Sound Environment-Techniques and Applications of Wave-Based Acoustics-

  日本建築学会

  Joint work, Oct. 2011, Japanese, ISBN: 4818927074

• 低周波数の吸音性能を強化するマイクロスリット共鳴器を埋め込んだメタポーラス吸音体−理論モデルの構築と吸音最適化−

  藤井倫太郎, 奥園健

  日本音響学会建築音響研究委員会, Jan. 2025, Japanese, 本論文では流れ抵抗率の低い薄い多孔質材料の低周波の吸音強化に効 果的な単純形状のサブ波長メタポーラス吸音体を理論モデルとともに提案する．提 案するメタポーラス吸音体は，多孔質材料内にサブ波長マイクロスリット共鳴器を戦略的に局所配置したユニットセルからなる周期的構造を持つ．提案する 3 種類のユニットセルのうち，吸音性能の異なる 2 つを組みわせることで互いの吸音能力を補完し広帯域に高い吸音を達成する．まず，提案する理論モデルの妥当性を数値解析，および，音響管実験により示す．次に，理論を遺伝的アルゴリズム最適化と組み合わせ設計した最適化メタポーラス準完全吸音体の吸音能力を示す., Domestic conference

  Oral presentation


• マイクロスリットを用いた音響メタサーフェスの吸音特性に3Dプリンタの造形精度が与える影響

  木村祐希, 奥園健

  日本音響学会秋季研究発表会, Sep. 2024, Japanese, Domestic conference

  Oral presentation


• 矩形ソニックブラックホール吸音体に関する基礎的研究

  上辻誠五, 奥園健

  日本音響学会秋季研究発表会, Sep. 2024, Japanese, Domestic conference

  Poster presentation


• 波動音響解析による室内音響予測の音響材料モデリングに関する研究―室容積の違いによるランダム入射吸音率モデルの適用性検証―

  田尻加奈子, 奥園健

  日本音響学会秋季研究発表会, Sep. 2024, Japanese, Domestic conference

  Poster presentation


• マイクロスリットを用いた音響メタサーフェス吸音体の簡易設計法-共鳴器群の吸音率の設計に関する検討-

  木村祐希, 奥園健

  日本音響学会秋季研究発表会, Sep. 2024, Japanese, Domestic conference

  Poster presentation


• マイクロスリット共鳴器を埋め込んだメタポーラス吸音体に関する研究−共鳴器の埋め込み位置を考慮した理論モデルの開発−

  藤井倫太郎, 奥園健

  日本音響学会秋季研究発表会, Sep. 2024, Japanese, Domestic conference

  Poster presentation


• ソニックブラックホール吸音体の理論モデルと積層造形法に関する基礎的検討

  上辻 誠五, 奥園 健

  日本建築学会大会, Aug. 2024, Japanese, Domestic conference

  Oral presentation


• 不完全結合共鳴器によるマイクロスリット音響メタサーフェス準完全吸音体の提案

  木村 祐希, 奥園 健

  日本建築学会大会, Aug. 2024, Japanese

  Oral presentation


• マイクロスリット共鳴器を埋め込んだメタポーラス吸音体の理論モデルの開発

  藤井 倫太郎, 奥園 健

  日本建築学会大会, Aug. 2024, Japanese, Domestic conference

  Oral presentation


• 不完全共鳴器の結合効果を用いた音響メタサーフェスによる 1/3 オクターブバンド準完全吸音体

  木村祐希, 奥園健

  令和6年度日本建築学会近畿支部研究発表会, Jun. 2024, Japanese, Domestic conference

  Oral presentation


• マイクロスリットを埋め込んだ音響メタサーフェスの吸音メカニズムに関する考察

  奥園健

  日本音響学会春季研究発表会, Mar. 2024, Japanese, Domestic conference

  Poster presentation


• 波動音響 VR による会議室の音環境シミュレーション -天井の吸音体レイアウトに関する検討-

  岡澤一葉, 奥園健

  日本音響学会春季研究発表会, Mar. 2024, Japanese, Domestic conference

  Poster presentation


• A simply designable microslit-embedded acoustics metasurface absorber

  Takeshi Okuzono

  日本音響学会建築音響研究委員会, Oct. 2023, English

  Oral presentation


• ネックを延長したマイクロスリットパネル共鳴器を埋め込んだメタポーラス吸音体に関する実験的研究

  藤井倫太郎, 奥園健

  日本音響学会秋季研究発表会, Sep. 2023, Japanese, Domestic conference

  Oral presentation


• 波動音響解析と 3D プリンタを用いたマイクロスリットによる音響メタサーフェス吸音体パネルの開発

  奥園健

  日本音響学会秋季研究発表会, Sep. 2023, Japanese, Domestic conference

  Oral presentation


• 波動音響による室内音響予測の音響材料モデリングに関する研究―局所作用性の材料を対象としたランダム入射吸音率モデルの適用性検証―

  田尻加奈子, 奥園健

  日本音響学会秋季研究発表会, Sep. 2023, Japanese, Domestic conference

  Oral presentation


• 波動音響 VR を用いた吸音材による室内音響調整効果の理解を深めるコンテンツの開発

  岡澤一葉, 奥園健, 吉田卓彌

  日本建築学会大会, Sep. 2023, Japanese, Domestic conference

  Oral presentation


• 先進的波動音響解析と高次アンビソニックスによる室内音響のバイノーラル可聴化

  吉田卓彌, 奥園健, 阪上公博

  日本建築学会大会, Sep. 2023, Japanese, Domestic conference

  Oral presentation


• Application of a parallel explicit time-domain FEM to binaural auralization of large-scale architectural space

  Takumi Yoshida, Takeshi Okuzono, Kimihiro Sakagami

  2023 Spring Meeting Acoustical Society of Japan, Mar. 2023, Japanese, Domestic conference


• Wave-based acoustics simulation of room acoustics for accurate and efficient visualization and auralization -PUFEM and time-domain FEM-

  Takeshi Okuzono, Takumi Yoshida

  2023 Spring Meeting Acoustical Society of Japan, Mar. 2023, Japanese, Domestic conference

  Oral presentation


• A parallel explicit time-domain FEM with cloud computing for room acoustics simulation

  Takumi Yoshida, Takeshi Okuzono, Kimihiro Sakagami

  2022 Autumn Meeting Acoustical Society of Japan, Sep. 2022, Japanese, Domestic conference

  Oral presentation


• A basic study on the design of a dotted-art heterogeneous MPP

  Kimihiro Sakagami, Midori Kusaka, Takeshi Okuzono

  2022 Autumn Meeting Acoustical Society of Japan, Sep. 2022, Japanese, Domestic conference

  Oral presentation


• Finite Element Modeling for Predicting Sound Insulation Performance of Single Fixed Windows on Laboratory Environment

  Marie Mimura, Takeshi Okuzono, Kimihiro Sakagami

  2022 Autumn Meeting Acoustical Society of Japan, Sep. 2022, Japanese, Domestic conference

  Oral presentation


• Sound insulation prediction of single fixed window in laboratory environment with FEM

  三村 茉莉絵, 奥園 健, 阪上 公博

  日本音響学会建築音響研究委員会, Aug. 2022, Japanese, 本稿では，実験室環境における単板固定窓のランダム入射音響透過損 失を予測するための，効率的な数値モデルについて議論した．入射条件として理想的な拡散入射を仮定した上で，3 種の FEM モデルによる音響透過損失の予測値をサイズの異なる 5 種類の単板固定窓の実測値と比較し，予測精度と計算コストを議論した．まず，窓部のみを離散化するモデルについて，2 種類の損失係数の与え方で音響透過損失を実測値と比較した．次に，窓部近傍の入射側・透過側空間を半自由空間として離散化することで，窓周辺のニッシェまで含めた強連成モデルによる 1 kHz 以下での音響透過損失の予測精度を検証した．最後に，ニッシェを含めた弱連成モデルの適用性を検証し，強連成モデルと概ね同等の精度でより効率的な予測が可能であることを明らかにした．, Domestic conference

  Oral presentation


• Large-scale room acoustics simulation using explicit time-domain FEM

  吉田 卓彌, 奥園 健, 阪上 公博

  日本音響学会建築音響研究委員会, Aug. 2022, Japanese, 波動音響学に基づく新しい室内音場予測手法として陽的時間領域 FEM による大規模音響解析手法を提案する．提案法は時空間離散化誤差を最適化することで音圧場の高精度な近似を可能とし，各種吸音体を局所作用性の周波数依存吸音境界条件によりモデル化できる．さらに領域分割型の並列計算により高速な音場予測を実現している．まず，提案法の妥当性と計算性能のそれぞれを小立方体室を対象とした周波数領域 FEM と 2 次得精度の陰的 TD-FEM との比較により検証し，粗い時空間離散化でより高精度かつ高効率な解析がで きることを示す．次に，512 コアを用いた MPI-OpenMP ハイブリッド並列のもと，1 億 5 千万自由度のオーディトリアムモデル内の 3 kHz までの周波数成分を含む 3 s 間のインパルス応答を 9,000 s 以内に解析可能なことを示す．, Domestic conference

  Oral presentation


• Robustness and efficiency of 2D plane-wave-enriched FEM for room acoustics simulation

  奥園 健, 向江 俊一, 阪上 公博

  日本音響学会建築音響研究委員会, Apr. 2022, Japanese, Japan, 平面波エンリッチメントを用いた PUFEM(PW-FEM)の室内音響解析における頑健性と従来の 1 次と 2 次 FEM に対する効率について議論する。形状の複雑さの異なる 2 種類のオフィスモデルを設定し、室形状の複雑さとメッシュの 空間分解能が解析の精度と頑健性に与える影響を参照解との比較により検証した。 主たる結果として、メッシュの最大要素サイズを解析上限周波数の波長程度とすることで、PW-FEM は広帯域に渡り、より高い頑健性を示すことを明らかにした。さらに、従来 FEM に比べ精度とメモリの観点から PW-FEM の優位性を示すとともに、2 次 FEM と比較して、PW-FEM は長時間に渡り高精度なインパルス応答波形を保つことを明らかにした。

  Oral presentation


• Sound insulation characteristics of small fixed windows in a laboratory and prediction with an existing theory

  Mimura Marie, Tsukamoto Yohei, Tomikawa Yoshihiro, Okuzono Takeshi, Sakagami Kimihiro

  日本音響学会建築音響研究委員会, Mar. 2022, Japanese, Japan, 遮音性の高い窓の効率的な開発には、高精度な窓の遮音性能の予測技術 が不可欠である．本稿では，窓の遮音性能の予測技術構築のファーストステップとして，最も構造が単純なFIX 窓を対象とし，実寸大でサイズの異なる5種類の窓の音響透過損失，振動特性，総合損失係数を実験室において測定し，窓サイズによる遮音性能の違いについて分析を行った．さらに，測定した総合損失係数を用いるこ とで，単一板の音響透過損失を予測する既存理論によって，実寸大の窓の遮音性能 を予測できるか検証した．結果として，実験室における FIX 窓の遮音性能はコインシデンス周波数以上では，明確なサイズ依存性を確認した．しかし，コインシデンス周波数以下では，最小サイズの窓をのぞき，サイズによる違いは確認されなかっ た．また，理論によるFIX窓の遮音特性の予測は，実測値の傾向を定性的には説明できるものの，定量的にはより小さな窓及びコインシデンス周波数近傍で大きな差が生じることが分かった．, Domestic conference

  Oral presentation


• A parallel explicit time-domain FEM for large-scale room acoustics simulation

  YOSHIDA Takumi, OKUZONO Takeshi, SAKAGAMI Kimihiro

  2022 Spring Meeting Acoustical Society of Japan, Mar. 2022, Japanese

  Oral presentation


• Acoustics simulation using 3D time-domain FEM considering wave nature of sound material-Part 2 extended-reaction model of microperforated panel-

  YOSHIDA Takumi, OKUZONO Takeshi, SAKAGAMI Kimihiro

  2022 Spring Meeting Acoustical Society of Japan, Mar. 2022, Japanese

  Oral presentation


• Acoustics simulation using 3D time-domain FEM considering wave nature of sound material-Part 1 Comparison with frequency-domian FEM-

  OKUZONO Takeshi, YOSHIDA Takumi, SAKAGAMI Kimihiro

  2022 Spring Meeting Acoustical Society of Japan, Mar. 2022, Japanese, Domestic conference

  Oral presentation


• Basic study on the applicability of plenum structure to doors: an experimental study with a modelled plenum door

  SAKAGAMI Kimihiro, MATSUMURA Soichiro, OKUZONO Takeshi

  2022 Spring Meeting Acoustical Society of Japan, Mar. 2022, Japanese

  Oral presentation


• Basic consideration of practical prediction method for sound insulation performance of double window (2) -Attempt to develop prediction method-

  TSUKAMOTO Yohei, TAMAI Kaoru, SAKAGAMI Kimihiro, OKUZONO Takeshi, TOMIKAWA Yoshihiro

  2022 Spring Meeting Acoustical Society of Japan, Mar. 2022, Japanese

  Oral presentation


• Basic consideration of practical prediction method for sound insulation performance of double window (1) -Application of existing theory of double wall-

  TSUKAMOTO Yohei, TAMAI Kaoru, SAKAGAMI Kimihiro, OKUZONO Takeshi, TOMIKAWA Yoshihiro

  2022 Spring Meeting Acoustical Society of Japan, Mar. 2022, Japanese

  Oral presentation


• Construction of room acoustics database with wave-based acoustic modeling –Auralization of sound absorption effect in a meeting room–

  Okuzono Takeshi, Yoshida Takumi, Sakagami Kimihiro

  日本音響学会建築音響研究委員会, Sep. 2021, Japanese, 建築空間の用途に応じた快適な音環境の形成には、吸音材を適切に使 用した室内音響調整が必要である。しかし、吸音設計が不適切なため音環境に問題 のある建築空間がいまだに数多く存在している。この一因として、建築音響の非専門家には吸音による音環境調整の重要性が十分に理解されていないことが考えられる。本研究では、この現状を解決する一つの策として、様々な建築空間における多 様な吸音材の効果を聴感的に体験することを可能とする室内音響データベースの作成を考えた。本稿ではその端緒として、小会議室を対象に実施した基礎検討の結果を報告する。具体的には、代表的な多孔質吸音材であるグラスウールとカーテンに焦点をあて、時間領域の波動音響シミュレーションのひとつである時間領域有限要素法を用いて、いくつかの内装条件における室内インパルス応答を音響材料の周波数依存性と入射角依存性を考慮して計算し、吸音による室内音響調整の効果を聴き比べることができるコンテンツの作成を試みた。, Domestic conference

  Oral presentation


• Performance improvement of single-leaf MPP sound absorber with porous partitions

  OKAYAMA Yuki, OKUZONO Takeshi, SAKAGAMI Kimihiro

  2021 Autumn Meeting Acoustical Society of Japan, Sep. 2021, Japanese

  Oral presentation


• An explicit time-domain FEM for room acoustic simulations using modified Adams method-Implementation of frequency-dependent absorption boundaries-

  SUGIMOTO Yui, YOSHIDA Takumi, OKUZONO Takeshi, SAKAGAMI Kimihiro

  2021 Autumn Meeting Acoustical Society of Japan, Sep. 2021, Japanese

  Oral presentation


• Partition of Unity FEM based room acoustic simulations -Study on robust plane-wave number setup-

  MUKAE Shunichi, OKUZONO Takeshi, SAKAGAMI Kimihiro

  2021 Autumn Meeting Acoustical Society of Japan, Sep. 2021, Japanese

  Oral presentation


• Room acoustic modeling with time-domain FEM including a frequency-dependent absorption boundary–Comparison with frequency-domain FEM–

  Takeshi Okuzono, Takumi Yoshida, Kimihiro Sakagami

  日本音響学会建築音響研究委員会, Mar. 2021, Japanese, 波動音響解析による高精度な室内音場予測のためには，材料の吸音特性の周波数依存性を考慮した吸音境界条件の使用が不可欠である。しかし，時間領域 における吸音境界条件には畳み込みが含まれることから，効率的な実装が必要となる。本論文では，補助微分方程式法を用いて吸音境界の周波数依存性を考慮した陰的時間領域FEMの性能を周波数依存性を厳密に反映可能な周波数領域FEMとの比較から明らかにする。音響管問題による時間領域FEMがもつ離散化誤差特性の検証から，時間領域FEMの離散化誤差の大きさは多孔質材の流れ抵抗率に依存し，その収束率は周波数領域 FEMと同様の2に近似すること，時間刻み幅を小さくす るにつれ周波数領域FEMの結果へと収束すること，を明らかにする。さらに実大の2次元オフィス，コンサートホールモデルを用いて，時間領域FEMは周波数領域FEMと同等の精度の解析を約 7 倍 ∼18 倍高速に計算できることを示す。

  Oral presentation


• Basic study on 3D room acoustics simulation using plane-wave-enriched FEM

  Kanako Tamaru, Takeshi OkKuzono, Shunichi Mukae, Kimihiro Sakagami

  2021 Spring Meeting Acoustical Society of Japan, Mar. 2021, Japanese, Domestic conference

  Oral presentation


• Study on practical predicting sound insulation performance of a single-leaf window (2)

  Kaoru TAMAI, Kimihiro SAKAGAMI, Takeshi OKUZONO, Yohei TSUKAMOTO

  2021 Spring Meeting Acoustical Society of Japan, Mar. 2021, Japanese, Domestic conference

  Oral presentation


• Study on practical predicting sound insulation performance of a single-leaf window (1)

  Yohei TSUKAMOTO, Kaoru TAMAI, Kimihiro SAKAGAMI, Takeshi OKUZONO

  2021 Spring Meeting Acoustical Society of Japan, Mar. 2021, Japanese, Domestic conference

  Oral presentation


• Basic study on prediction of sound insulation performance of a single-leaf window

  Yohei Tsukamoto, Kimihiro Sakagami, Takeshi Okuzono, Yoshihiro Tomikawa

  日本音響学会建築音響研究委員会, Jul. 2020, Japanese, Domestic conference

  Oral presentation


• Effect of deviation of the parameters by manufacturing accuracy of an MPP on its acoustic properties: Trial production of MPPs of various hole shapes by 3D printing

  Kimihiro Sakagami, Midori Kusaka, Takeshi Okuzono, Shinsuke Nakanishi

  日本音響学会建築音響研究委員会, Jun. 2020, Japanese, 本研究では，３D プリンタによって作成したMPP の製作精度が，MPP の吸音特性に及ぼす影響について，実験および理論の両面から 基礎的な検討を行った．MPP については，従来に比べてコストの低廉化や工程の簡略化に向けて，近年は多種多様な試作事例が報告されており，３D プリンタによる試作検討事例も報告されている．こうした場合，一般的な穴あけ加工以外の手法では，その製作精度が問題となる場合も多いが，その影響について詳しい考察を行った研究例はごく少数である．本研究では，民生用に広く普及している熱溶解積層型３D プリンタによって各種形態のMPP の作成を試み，その精度について検討し，誤差が音響特性および理論による予測精度に及ぼす影響について，基礎的な考察を試みた．その結果，熱溶解積層型３D プリンタによるMPP 作成は精度的には誤差が大きいものの，一定の吸音性能を示すが，理論値との一致は悪いため設計や予測の際には注意を要することを論じた．, Domestic conference

  Oral presentation


• Numerical prediction of reverberation absorption coefficient of permeable membrane sound absorbers with time-domain FEM

  奥園健, 阪上公博

  日本音響学会建築音響研究委員会, May 2020, Japanese, 通気性膜（各種天然・化学繊維素材の通気性のある薄い織編物・不織布）は繊維・製造方法・加工技術の組み合わせで様々な機能設計が可能な魅力的な吸音材料であり、近年、様々な通気性膜吸音体が開発され室内の音響調整に活用されている。本稿では、著者らの先行研究に基づき通気性膜を時間領域FEM解析でモデル化する方法を提示するとともに、残響室法吸音率の測定を直接的に時間領域で模擬し、最も古典的な単一通気性膜吸音体を対象として数値解析値を実測値ならびに理論値と比較した結果を示す。汎用繊維であるPET, PP, ガラス繊維素材の材料特性の異なる8 種類の通気性膜について検討し、結果として、提示した時間領域解析手法により、通気性膜の材料特性の違いによる残響室法吸音率の大小関係を予測できることを示す。, International conference

  Oral presentation


• Sound field analysis using plane wave enriched FEM Part2-Comparison of performance between low-order and high-order elements-

  Mukae shunichi, Okuzono Takeshi, Tamaru Kanako, Sakagami Kimihiro

  2020 Spring Meeting Acoustical Society of Japan, Mar. 2020, Japanese, Domestic conference

  Oral presentation


• 平面波エンリッチメントを用いたPartition of Unity FEMによる室内音場解析

  奥園健, 田丸加奈子, 向江俊一, 阪上公博

  日本音響学会建築音響研究委員会, Jan. 2020, Japanese, Helmholtz方程式の一般解を用いて場の近似を強化し、Q-refinementによって粗いメッシュを用いて高周波数まで解析を行うPartition of Unity FEM(PUFEM)に基づく音響数値解析手法を室内音場解析手法に導入する。まず一般解として平面波をエンリッチメントに用いるPUFEMの基礎理論を示す。次に2種の2次元室内音場を対象に、空間4次精度のFEMを参照解として、従来の空間2次精度FEMとの比較からPUFEMの精度ならびにQ-refinementの有用性を明らかにする。結果として、PUFEMは単一の粗いメッシュを用いて、従来FEMに比べ、少なくともオーダー1/100以下の著しく少ない自由度で広帯域の周波数応答をより高精度に計算できることを示す。

  Oral presentation


• Numerical Study on Improvement of Prediction of Acoustic Parameter in Room

  YOSHIDA Tsuyoshi, OTSURU Toru, TOMIKU Reiji, OKUZONO Takeshi, AZECHI Yoshiki

  日本建築学会研究報告. 九州支部. AIJ Kyushu Chapter architectural research meeting. 日本建築学会九州支部 編, Mar. 2015, Japanese, Architectural Institute of Japan


• Numerical Study on the Measurement of Absorption Coefficient in a Reverberation Room : Uncertainties of Reverberation Time

  AZECHI Yoshiki, OTSURU Toru, TOMIKU Reiji, OKAMOTO Noriko, OKUZONO Takeshi, YOSHIDA Tsuyoshi

  日本建築学会研究報告. 九州支部. AIJ Kyushu Chapter architectural research meeting. 日本建築学会九州支部 編, Mar. 2015, Japanese, Architectural Institute of Japan


• 40130 Sound absorpton measurement of materials using ensemble averaging technique : Part1 Calibration of pressure-particle velocity sensor using an acoustic tube

  UEDA Emi, OTSURU Toru, TOMIKU Reiji, OKUZONO Takeshi, YANACHI Masatoshi

  Summaries of technical papers of annual meeting, Sep. 2014, Japanese, Architectural Institute of Japan


• 40122 Room shape modeling for sound field analysis of rooms : An investigation on the depth of building members using time-domain finite element method

  MATSUMOTO Chikashi, OTSURU Toru, TOMIKU Reiji, OKAMOTO Noriko, OKUZONO Takeshi, HOSHI Kazuma, ITAI Ken

  Summaries of technical papers of annual meeting, Sep. 2014, Japanese, Architectural Institute of Japan


• 40125 Numerical study on the measurement of absorption coefficient in reverberation rooms : Investigation on errors of measured values and variations of reverberation times

  AZECHI Yoshiki, OTSURU Toru, TOMIKU Reiji, OKAMOTO Noriko, OKUZONO Takeshi, YOSHIDA Tsuyoshi

  Summaries of technical papers of annual meeting, Sep. 2014, Japanese, Architectural Institute of Japan


• 40124 Improvement of accuracy of absorption coefficient measured in a reverberation room by time domain finite element sound field analysis : Classification of the sound fields on sound incident energy on specimen

  YOSHIDA Tsuyoshi, OTSURU Toru, TOMIKU Reiji, OKAMOTO Noriko, OKUZONO Takeshi, AZECHI Yoshiki

  Summaries of technical papers of annual meeting, Sep. 2014, Japanese, Architectural Institute of Japan


• 40132 Application of in-situ measurement method of absorption characteristics of materials using ensemble averaging : Acoustic improvement of a cafe by ceiling repairment

  NAKAMURA Asami, OTSURU Toru, TOMIKU Reiji, OKUZONO Takeshi

  Summaries of technical papers of annual meeting, Sep. 2014, Japanese, Architectural Institute of Japan


• 40131 Sound absorption measurement of materials using ensemble averaging technique : Part 2 Calibration of pressure-particle velocity sensor by piston on a sphere method

  YANACHI Masatoshi, OTSURU Toru, TOMIKU Reiji, OKUZONO Takeshi, UEDA Emi

  Summaries of technical papers of annual meeting, Sep. 2014, Japanese, Architectural Institute of Japan


• 40123 Room shape modeling for sound field analysis of room on wave-based acoustic simulations using time-domain finite element method : Part 4 Difference of acoustic elements

  ITAI Ken, OTSURU Toru, TOMIKU Reiji, OKAMOTO Noriko, OKUZONO Takeshi, MATSUMOTO Chikashi

  Summaries of technical papers of annual meeting, Sep. 2014, Japanese, Architectural Institute of Japan


• 40085 Basic study on the effects of fractions of gas and liquid phases to the acoustic characteristics of sandy soil

  OSHIMA Takuya, OKUZONO Takeshi, HIRAGURI Yasuhiro

  Summaries of technical papers of annual meeting, Sep. 2014, Japanese, Architectural Institute of Japan


• 40086 Basic study on correspondence of absorption characteristics of ground surfaces by in-situ measurement and their spectral radiance obtained by airborne hyperspectral image

  WAKAMATSU Kei

  Summaries of technical papers of annual meeting, Sep. 2014, Japanese, Architectural Institute of Japan


• 4-3-c Basic study on correspondence of absorption characteristics of ground surfaces by in-situ measurement and their spectral radiance obtained by airborne hyperspectral imagery

  WAKAMATSU Kei

  日本建築学会北陸支部研究報告集, Jul. 2014, Japanese, Architectural Institute of Japan


• Sound absorption measurement of materials using ensemble averaging technique : Application to the development of interior finish wood utilizing porous mortar

  KAMIMIZU Takaaki, OTSURU Toru, TOMIKU Reiji, OKAMOTO Noriko, OKUZONO Takeshi, YAMAGUCHI Makoto

  日本建築学会研究報告. 九州支部. AIJ Kyushu Chapter architectural research meeting. 日本建築学会九州支部 編, Mar. 2014, Japanese, Architectural Institute of Japan


• 414 Basic study on sound environment improvement in cafe : Acoustical renovation effect and measured absorption coefficients

  MATSUSHIMA Rikako, OTSURU Toru, TOMIKU Reiji, OKUZONO Takeshi

  日本建築学会研究報告. 九州支部. 2, 環境系, Mar. 2014, Japanese, Architectural Institute of Japan


• 404 Room shape modeling for sound field analysis of rooms on wave-based acoustic simulations using time-domain finite element method : An investigation on the depth of building component simplification

  AIHOSHI Hikaru, OTSURU Toru, TOMIKU Reiji, OKAMOTO Noriko, OKUZONO Takeshi, HOSHI Kazuma, ITAI Ken

  日本建築学会研究報告. 九州支部. 2, 環境系, Mar. 2014, Japanese, Architectural Institute of Japan


• Room Shape Modeling for Sound Field Analysis of Rooms using Time-Domain Finite Element Method(Part 6)Investigation on acoustic elements

  ITAI Ken, OTSURU Toru, TOMIKU Reiji, OKAMOTO Noriko, OKUZONO Takeshi, AIHOSHI Hikaru

  日本建築学会研究報告. 九州支部. AIJ Kyushu Chapter architectural research meeting. 日本建築学会九州支部 編, Mar. 2014, Japanese, Architectural Institute of Japan


• Numerical study on the measurement of absorption coefficient in a reverberation room : Errors and variations of measured values

  AZECHI Yoshiki, OTSURU Toru, TOMIKU Reiji, OKAMOTO Noriko, OKUZONO Takeshi, ADACHI Daisuke

  日本建築学会研究報告. 九州支部. AIJ Kyushu Chapter architectural research meeting. 日本建築学会九州支部 編, Mar. 2014, Japanese, Architectural Institute of Japan


• Improvement of accuracy of absorption coefficient measured in a reverberation room by time domain finite element sound field analysis : Study on sound incident energy on specimen and apply to actual measurement

  ADACHI Daisuke, OTSURU Toru, TOMIKU Reiji, OKAMOTO Noriko, OKUZONO Takeshi, AZECHI Yoshiki

  日本建築学会研究報告. 九州支部. AIJ Kyushu Chapter architectural research meeting. 日本建築学会九州支部 編, Mar. 2014, Japanese, Architectural Institute of Japan


• Ensemble averaged Absorption characteristics of materials using an in-situ technique : Investigation on measurement of reflective materials

  NAKANO Kazuki, OTSURU Toru, TOMIKU Reiji, OKUZONO Takeshi

  日本建築学会研究報告. 九州支部. AIJ Kyushu Chapter architectural research meeting. 日本建築学会九州支部 編, Mar. 2014, Japanese, Architectural Institute of Japan


• 40111 Numerical study on the measurement of absorption coefficient in a reverberation room by time domain finite element sound field analysis : Part2 Calculation of absorption coefficient in a reverberation room by corrected decay curves

  ADACHI Daisuke, OTSURU Toru, TOMIKU Reiji, OKAMOTO Noriko, OKUZONO Takeshi, AZECHI Yoshiki

  Summaries of technical papers of annual meeting, Aug. 2013, Japanese, Architectural Institute of Japan


• 40106 Basic investigations on sound field analysis in rooms using image processing technique : Part2 Implementation of a technique for measuring 3D coordinate of a room using fisheye lens

  TAKIKAWA Takashi, OTSURU Toru, TOMIKU Reiji, OKUZONO Takeshi, ODA Tomohiro

  Summaries of technical papers of annual meeting, Aug. 2013, Japanese, Architectural Institute of Japan


• 40110 Numerical study on the measurement of absorption coefficient in a reverberation room by time domain finite element sound field analysis : Part1 Investigation on correction of decay curve

  AZECHI Yoshiki, OTSURU Toru, TOMIKU Reiji, OKAMOTO Noriko, OKUZONO Takeshi, ADACHI Daisuke

  Summaries of technical papers of annual meeting, Aug. 2013, Japanese, Architectural Institute of Japan


• 40104 Room shape modeling for sound field analysis of rooms on wave-based acoustic simulations using time-domain finite element method : Part3 Investigations on window shape modeling

  AIHOSHI Hikaru, OTSURU Toru, TOMIKU Reiji, OKAMOTO Noriko, OKUZONO Takeshi, ITAI Ken

  Summaries of technical papers of annual meeting, Aug. 2013, Japanese, Architectural Institute of Japan


• 40105 Numerical study on in-situ measurement of absorption characteristics of architectural materials by time domain finite element method : Investigation on source material distance and mesurement error

  KAMIMIZU Takaaki, OTSURU Toru, TOMIKU Reiji, OKAMOTO Noriko, OKUZONO Takeshi, MATSUSHIMA Rikako

  Summaries of technical papers of annual meeting, Aug. 2013, Japanese, Architectural Institute of Japan


• 40115 Sound absorpton measurement of materials using ensemble averaging technique : Basic investigation on measurement of reflective materials

  NAKANO Kazuki, OTSURU Toru, TOMIKU Reiji, OKUZONO Takeshi, Kusno Asniawaty, YANACHI Masatoshi

  Summaries of technical papers of annual meeting, Aug. 2013, Japanese, Architectural Institute of Japan


• 40102 Room shape modeling for sound field analysis of rooms on wave-based acoustic simulations using time-domain finite element method : Part1 Settings of subjective evaluation experiments on listening to words and music

  OKAMOTO Noriko, OTSURU Toru, TOMIKU Reiji, OKUZONO Takeshi, ITAI Ken, AIHOSHI Hikaru

  Summaries of technical papers of annual meeting, Aug. 2013, Japanese, Architectural Institute of Japan


• 40103 Room shape modeling for sound field analysis of rooms on wave-based acoustic simulations using time-domain finite element method : Part2 Results of subjective evaluation experiments on listening to words and music

  ITAI Ken, OTSURU Toru, TOMIKU Reiji, OKAMOTO Noriko, OKUZONO Takeshi, AIHOSHI Hikaru

  Summaries of technical papers of annual meeting, Aug. 2013, Japanese, Architectural Institute of Japan


• Room Shape Modeling for Sound Field Analysis of Rooms using Time-Domain Finite Element Method(Part 5)Window shape modeling

  AIHOSHI Hikaru, OTSURU Toru, TOMIKU Reiji, OKAMOTO Noriko, OKUZONO Takeshi

  日本建築学会研究報告. 九州支部. AIJ Kyushu Chapter architectural research meeting. 日本建築学会九州支部 編, Mar. 2013, Japanese, Architectural Institute of Japan


• Relationship between Dispersion Error and Accuracy of Objective Room Acoustics Measures in Time-Domain Finite Element Sound Field Analysis of Rooms

  OKUZONO Takeshi, OTSURU Toru, TOMIKU Reiji, OKAMOTO Noriko

  日本建築学会研究報告. 九州支部. AIJ Kyushu Chapter architectural research meeting. 日本建築学会九州支部 編, Mar. 2013, Japanese, Architectural Institute of Japan


• Ensemble averaged absorption characteristics of materials using an in-situ technique : Basic investigation on measurement of reflective materials

  NAKANO Kazuki, OTSURU Toru, TOMIKU Reiji, OKUZONO Takeshi

  日本建築学会研究報告. 九州支部. AIJ Kyushu Chapter architectural research meeting. 日本建築学会九州支部 編, Mar. 2013, Japanese, Architectural Institute of Japan


• Room Shape Modeling for Sound Field Analysis of Rooms using Time-Domain Finite Element Method(Part 4)An evaluation by subjective experiments : Audition of single word and music sound

  KITAMURA Naoya, OTSURU Toru, TOMIKU Reiji, OKAMOTO Noriko, OKUZONO Takeshi

  日本建築学会研究報告. 九州支部. AIJ Kyushu Chapter architectural research meeting. 日本建築学会九州支部 編, Mar. 2013, Japanese, Architectural Institute of Japan


• Finite element sound field analysis on the measurement of absorption coefficient in a reverberation room : Investigation on correction of decay curve

  ADACHI Daisuke, OTSURU Toru, TOMIKU Reiji, OKAMOTO Noriko, OKUZONO Takeshi

  日本建築学会研究報告. 九州支部. AIJ Kyushu Chapter architectural research meeting. 日本建築学会九州支部 編, Mar. 2013, Japanese, Architectural Institute of Japan


• Basic investigations on sound field analysis in rooms using image processing technique : Implementation of a technique for measuring 3D coordinate of a room using fish eye lens

  ODA Tomohiro, OTSURU Toru, TOMIKU Reiji, OKUZONO Takeshi

  日本建築学会研究報告. 九州支部. AIJ Kyushu Chapter architectural research meeting. 日本建築学会九州支部 編, Mar. 2013, Japanese, Architectural Institute of Japan


• Basic study on sound environment improvement in cafe space

  MATSUSHIMA Rikako, OTSURU Toru, TOMIKU Reiji, OKUZONO Takeshi

  日本建築学会研究報告. 九州支部. AIJ Kyushu Chapter architectural research meeting. 日本建築学会九州支部 編, Mar. 2013, Japanese, Architectural Institute of Japan


• 40074 Numerical investigation of in-situ measurement of absorption characteristics of materials : Relationship between sound source condition and measurement error

  MATSUSHIMA Rikako, OTSURU Toru, TOMIKU Reiji, OKAMOTO Noriko, OKUZONO Takeshi

  Summaries of technical papers of annual meeting, Sep. 2012, Japanese, Architectural Institute of Japan


• 40082 Room Shape Modeling of Time Domain Sound Field Analysis by Finite Element Method : Basic evaluation of accuracy using subjective experiment

  AIHOSHI Hikaru, OTSURU Toru, TOMIKU Reiji, OKUZONO Takeshi, OKAMOTO Noriko

  Summaries of technical papers of annual meeting, Sep. 2012, Japanese, Architectural Institute of Japan


• 40078 Basic investigations of sound field analysis in rooms using image processing

  ODA Tomohiro, OTSURU Toru, TOMIKU Reiji, OKUZONO Takeshi, NAKANO Kazuki

  Summaries of technical papers of annual meeting, Sep. 2012, Japanese, Architectural Institute of Japan


• 40076 Sound field analysis of rooms by time-domain finite-element method using modified integration rule : Applicability to sound field analysis involving distorted elements and finite impedance boundary conditions

  OKUZONO Takeshi, OTSURU Toru, TOMIKU Reiji, OKAMOTO Noriko

  Summaries of technical papers of annual meeting, Sep. 2012, Japanese, Architectural Institute of Japan


• 40073 Improvement of accuracy of absorption coefficient measured in reverberation room : Comparison of the results obtained by sound ray method and time domain finite element method

  ADACHI Daisuke, OTSURU Toru, TOMIKU Reiji, OKAMOTO Noriko, OKUZONO Takeshi

  Summaries of technical papers of annual meeting, Sep. 2012, Japanese, Architectural Institute of Japan


• 405 Basic investigation on sound field prediction using photogrammetry

  ODA Tomohiro, OTSURU Toru, TOMIKU Reiji, OKUZONO Takeshi, Yahya Mush Nizam bin, NAGASAWA Toshiki

  日本建築学会研究報告. 九州支部. 2, 環境系, Mar. 2012, Japanese, Architectural Institute of Japan


• 402 Finite element sound field analysis on the measurement of sound absorption coefficient in a reverberation room : Comparison with sound ray method

  NAKAGAWA Tatsuya, OTSURU Toru, TOMIKU Reiji, OKAMOTO Noriko, OKUZONO Takeshi

  日本建築学会研究報告. 九州支部. 2, 環境系, Mar. 2012, Japanese, Architectural Institute of Japan


• 403 Expansion of application range of time-domain finite-element method using acoustic elements with modified integration rule

  MARUYAMA Kazunari, OTSURU Toru, TOMIKU Reiji, OKUZONO Takeshi, OKAMOTO Noriko

  日本建築学会研究報告. 九州支部. 2, 環境系, Mar. 2012, Japanese, Architectural Institute of Japan


• 40151 Ensemble averaged absorption characteristics of materials using an in-situ technique : Investigation on the measurement modeling by time domain fininte element method

  SHIBATA Takahiro, OTSURU Toru, TOMIKU Reiji, OKAMOTO Noriko, OKUZONO Takeshi

  Summaries of technical papers of Annual Meeting Architectural Institute of Japan. D-1, Environmental engineering I, Room acoustics and acoustic environment noise and solidborne sound environmental vibration light and color water supply and drainage water environment urban installation and environmental management environmental psychology and physiology environmental design electro-magnetic environment, Jul. 2011, Japanese, Architectural Institute of Japan


• 40146 Finite element sound field analysis on correction value of absorption coefficient in a reverberation room : Part 1 Study on sound incident energy on specimen

  TOMIKU Reiji, OTSURU Toru, OKAMOTO Noriko, OKUZONO Takeshi, NAKAGAWA Tatsuya

  Summaries of technical papers of Annual Meeting Architectural Institute of Japan. D-1, Environmental engineering I, Room acoustics and acoustic environment noise and solidborne sound environmental vibration light and color water supply and drainage water environment urban installation and environmental management environmental psychology and physiology environmental design electro-magnetic environment, Jul. 2011, Japanese, Architectural Institute of Japan


• 40145 Investigations of sound field prediction in rooms by handy methods : Implementation of neural network model and image processing

  ODA Tomohiro, Musli Nizam Yahya, OTSURU Toru, TOMIKU Reiji, OKAMOTO Noriko, OKUZONO Takeshi

  Summaries of technical papers of Annual Meeting Architectural Institute of Japan. D-1, Environmental engineering I, Room acoustics and acoustic environment noise and solidborne sound environmental vibration light and color water supply and drainage water environment urban installation and environmental management environmental psychology and physiology environmental design electro-magnetic environment, Jul. 2011, Japanese, Architectural Institute of Japan


• 40147 Finite element sound field analysis on correction value of absorption coefficient in a reverberation room : Part 2 Basic study on correction method

  NAKAGAWA Tatsuya, OTSURU Toru, TOMIKU Reiji, OKAMOTO Noriko, OKUZONO Takeshi

  Summaries of technical papers of Annual Meeting Architectural Institute of Japan. D-1, Environmental engineering I, Room acoustics and acoustic environment noise and solidborne sound environmental vibration light and color water supply and drainage water environment urban installation and environmental management environmental psychology and physiology environmental design electro-magnetic environment, Jul. 2011, Japanese, Architectural Institute of Japan


• 40139 Room Shape Modeling of Time Domain Sound Field Analysis by Finite Element Method : A method of room shape modeling and evaluation index

  KITAMURA Naoya, OTSURU Toru, TOMIKU Reiji, OKAMOTO Noriko, OKUZONO Takeshi

  Summaries of technical papers of Annual Meeting Architectural Institute of Japan. D-1, Environmental engineering I, Room acoustics and acoustic environment noise and solidborne sound environmental vibration light and color water supply and drainage water environment urban installation and environmental management environmental psychology and physiology environmental design electro-magnetic environment, Jul. 2011, Japanese, Architectural Institute of Japan


• 40138 Sound field analysis of rooms by time domain finite element method : Application of an acoustic element using modified integration rule

  MARUYAMA Kazunari, OTSURU Toru, TOMIKU Reiji, OKUZONO Takeshi, OKAMOTO Noriko

  Summaries of technical papers of Annual Meeting Architectural Institute of Japan. D-1, Environmental engineering I, Room acoustics and acoustic environment noise and solidborne sound environmental vibration light and color water supply and drainage water environment urban installation and environmental management environmental psychology and physiology environmental design electro-magnetic environment, Jul. 2011, Japanese, Architectural Institute of Japan


• 有限要素法による実在建築空間の音場予測

  奥園健, 大鶴徹, 富来礼次, 岡本則子, 巳之口俊史

  九州大学情報基盤研究開発センター全国共同利用システム広報, Oct. 2009, Japanese

• 日本騒音制御工学会


• 日本音響学会


• 日本建築学会

• Virtual prototyping of architectural sound environment design techniques using acoustic metamaterial sound absorbers

  奥園 健

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (C), Kobe University, Apr. 2024 - Mar. 2027, Principal investigator


• Construction of practical boundary modeling for wave acoustic simulation in a room

  富来 礼次, 岡本 則子, 大鶴 徹, 奥園 健

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (C), Oita University, Apr. 2023 - Mar. 2026, Coinvestigator

  Others


• Construction of wave-based room-acoustics database for comfortable acoustic environment design

  Takeshi Okuzono, Takumi Yoshida

  Ono Charitable Trust for Acoustics, 研究助成, Apr. 2022 - Mar. 2023, Principal investigator

  Others


• Development of wave-based numerical methods able to predict room acoustics at full audible ranges

  Okuzono Takeshi

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C), Grant-in-Aid for Scientific Research (C), Kobe University, Apr. 2020 - Mar. 2023, Principal investigator

  本研究の目的は、建築音響分野において、従来困難とされてきた、可聴域全域、かつ、高精度な境界条件に基づく室内音響予測を可能とする波動数値解析技術の確立である。具体的にはPartition of Unity FEM (PUFEM)による室内音響解析手法の開発を試みている。令和3年度は、平面波エンリッチメントを用いたPUFEMによる音響解析手法の頑健性に関する検証として、2種の平面波エンリッチメントの方法の比較、及び解析モデルが持つ室形状の複雑さと使用するメッシュの空間分解能が解析の精度と頑健性に与える影響を検証した。最終的に多周波数応答解析において、頑健性と効率性を両立した解析を行うためのメッシュ生成に関する提案を行った。得られた成果は以下の通りである。 1.Constant-qとVariable-qと呼ばれる2種の平面波エンリッチメントを用いるPUFEMの頑健性を、拡散体を含む2次元オフィス内音場を対象に比較し、Variable-qアプローチがより高い頑健性を持つことを明らかにした。 2.より頑健な解析を行うには、「メッシュにおける最大要素サイズを上限周波数の波長と同程度とした方がよい」ことを明らかにした。この指針は計算コストの観点からも推奨できる。 3.従来の1次と2次FEMと比較したPUFEMの優位な点として、室内音響評価に不可欠なインパルス応答波形を長時間に渡って高精度に近似可能であることを明らかにした。一方、2次FEMはその離散化誤差特性により、時間の経過に従い波形の劣化が生じることを示した。 上記の成果は英文学術雑誌ACOUSTICSへ投稿し、2022年1月にオンライン掲載された。また、前年度投稿済みであった論文2編がそれぞれAcoustical Science and TechnologyとApplied Acousticsへ掲載され、合計3編の学術論文の掲載を達成した。


• Study on room acoustic simulations using time-domain finite element method able to deal with frequency and incident angle dependence of acoustic materials

  公益財団法人鹿島学術振興財団, 研究助成, Apr. 2021 - Mar. 2022, Principal investigator

  This project aims to develop novel wave-based acoustic simulation methods based on the time-domain finite-element method (FEM) as a highly accurate room acoustics design tool. As the salient point of novelty of the project, we proposed two time-domain FEMs that can consider frequency and incident angle dependence of acoustic materials. A proposed implicit time-domain FEM can compute indoor sound environments with significantly higher efficiency while keeping accuracy compared to frequency-domain FEM, which is a standard selection for acoustic simulations. Also, the presented implicit formulation has a high generality that can apply to any finite element with different shapes and polynomial orders. Another domain decomposition method (DDM) based parallel explicit time-domain FEM, which uses a unique formulation, can realize further high-speed computation under a high-performance computing system with many CPU cores. A basic performance examination with 512 CPU cores showed that the proposed DDM based explicit time-domain FEM could simulate room impulse response of a large auditorium with 3 s time length, including frequency component up to 3 kHz within 9000 s.

  Others


• 非拡散音場の音響調整のための吸音処理手法の開発

  奥園 健

  学術研究助成基金助成金／若手研究(B), Apr. 2017 - Mar. 2020, Principal investigator

  Competitive research funding


• 広域環境騒音伝搬予測のための地表面音響特性時空間変動モデルの確立

  大嶋 拓也

  日本学術振興会, 科学研究費助成事業／基盤研究(B), Apr. 2016 - Mar. 2020

  Competitive research funding


• 波動数値シミュレータによる次世代吸音構造を有する建築の音響設計手法の開発

  奥園 健

  学術研究助成基金助成金／若手研究(B), Apr. 2015 - Mar. 2017, Principal investigator

  Competitive research funding


• 次世代音響設計のための大規模有限要素数値解析技術の確立

  OKUZONO Takeshi

  Japan Society for the Promotion of Science, Grant-in-Aid for JSPS Fellows, 特別研究員奨励費, 大分大学, Apr. 2009 - Mar. 2010, Principal investigator

  容積40,000m^3の建築空間の4kHz周波数領域までの精密な音場予測を実用時間内に可能とする時間領域有限要素解析手法の開発を目的とし、本年度は以下の成果を得た。 1.効率的な時間領域有限要素解析手法の開発:空間離散化のための音響要素の高性能化を図ることで計算の効率化を達成した。まず、8節点6面体要素を用いた有限要素解析手法へ修正積分則を適用し、3次元分散誤差解析・数値実験を通して従来要素に対する有効性を示した。また、従来、時間領域解析では正方形要素へと適用範囲が限定されていた修正積分則が直接時間積分法にFox-Goodwin法を用いることで直方体要素に対しても適用可能であることを明らかにすると共に、同積分則を用いることで反復解法の収束性が向上することを明らかにした。さらに、スプライン関数を用いた27節点6面体要素の性能を向上させる1次元分散誤差解析を用いた数値積分点の修正法を提案し、その基礎的な有用性を理論ならびに数値実験の両面から示した。なお、提案法は周波数領域解析を対象に提案したが、時間領域解析においても適用可能である。 2.室形状モデリングの煩雑性の克服と各種吸音モデリングの構築:複雑な建築の室形状をどこまでモデル化する必要があるのかを明確にするため、直方体格子のサイズにより室形状の近似程度を定量化するモデル化手法を新たに考案した。同方法を用いて室形状の簡略化の程度と算出される解析結果(インパルス応答ならびに音響指標)の差異の関係について検討した。

  Competitive research funding

• 音場解析装置、音場解析方法及びプログラム

  吉田 卓彌, 奥園 健, 阪上 公博

  特願2021-008482, 22 Jan. 2021, 特許7496973, 31 May 2024, 株式会社安藤・間; 国立大学法人神戸大学

  Patent right


• 音場解析装置、音場解析方法及びプログラム

  吉田 卓彌, 奥園 健, 阪上 公博

  特願2021-008481, 22 Jan. 2021, 特許7496972, 31 May 2024, 株式会社安藤・間; 国立大学法人神戸大学

  Patent right


• 音場解析装置、音場解析方法及びプログラム

  吉田 卓彌, 奥園 健, 阪上 公博

  特願2019-135950, 24 Jul. 2019, 特許7285514, 25 May 2023, 株式会社安藤・間; 国立大学法人神戸大学

  Patent right


• 音場解析装置、音場解析方法及びプログラム

  吉田 卓彌, 奥園 健, 阪上 公博

  特願2019-235949, 24 Jul. 2019, 特許7285513, 25 May 2023, 株式会社安藤・間; 国立大学法人神戸大学, Domestic, Domestic

  Patent right