Kyushu University [Akira Omoto (Professor) Faculty of Design, Department of Acoustic Design]

Department of Design
Graduate School of Design

Department of Design
School of Design

Design Initiative for Diversity and Inclusion

Vice President

Dean of the School of Design

Dean of the Graduate School of Design

Dean of the Faculty of Design

Ph. D

Applied Acoustical Engineering

https://orcid.org/0000-0003-1906-1754

00years10months

After researching the application of active noise control to noise barriers and the adaptive algorithms necessary for the control, my recent research activities have focused on the measurement, evaluation, and control of relatively small-sized enclosed spaces. In the field of acoustics, my research can be classified into the fields of architectural acoustics, noise, and electroacoustics.

The keywords used in my previous publications are visualization of the sound field, analysis of the enclosed sound field, measurement of acoustical physical parameters, physical parameters with auditory filters, variable reflection acoustic wall system, active acoustic impedance control, and sound field reproduction.

From 2010 to 2015, I have been working on the construction of a sound field database as the main co-researcher of CREST "Development of a Sound Field Sharing System to Support Creative and Exchange Activities Using Music" (PI: Shiro Ise, Kyoto University).

Since FY2013, the main research topic focused on how to rationally integrate engineering-accurate methods and artistic production methods in sound field reproduction, and since FY2017, the study from the viewpoint of the social implementation of these sound field reproduction systems was added. From FY2020 onward, acoustics and welfare engineering were integrated into our activities, with the aim of directly utilizing our systems for human welfare.

As for education, I am in charge of lectures on acoustical theory related to basic physical acoustics, room acoustics, and nonlinear vibration theory (assigned), and my own lecture notes are prepared and distributed to students. In addition, in graduate school, I have lectures on the principle and control method of active control. In addition, I support the project promotion of the hall management engineer training program from an engineering point of view, and I am in charge of the special lecture on hall engineering.

Research Interests

Measurement, evaluation, control, and reproduction of sound field
keyword : Sound Field Measurement, Sound Field Evaluation, Sound Field Control, Sound Field Reproduction
2010.10Measurement, evaluation and control of the acoustic characteristics of small sized enclosed spaces, such as recording studios..

Academic Activities

Reports

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Papers

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1.	Ryoko Hara, Takahiro Iwami, Akira Omoto, Subjective evaluation of auralization using a directional sound source that simulates a trumpet, Acoustical Science and Technology, Acoustical Letter accepted for publication, 2022.03.
2.	Ryoko Hara, Takahiro Iwami, Hiroshi Kashiwazaki, Akira Omoto, Synthesis of musical instrument directivities with a single common loudspeaker (L), The Journal of the Acoustical Society of America, https://doi.org/10.1121/10.0006660, 150, 4, 2549-2552, Letter, 2021.10, [URL], This letter synthesizes musical instrument directivities by sequentially rotating a loudspeaker through multiple orientations. The synthesis is conducted in a spherical harmonic domain using the actual measured directivity of a commercial loudspeaker and an open database of musical instrument directivities. The letter further proposes a practically useful set of 26 loudspeaker orientations named Step45, which can be used to reproduce the target directivity as well as if the orientations were determined adopting mathematical methods that give equilibrium configurations..
3.	Akira Omoto, Hiroshi Kashiwazaki, Hypotheses for constructing a precise, straightforward, robust and versatile sound field reproduction system, Acoustical Science and Technology, https://doi.org/10.1250/ast.41.151, 41, 1, 151-159, Invited Review, 2020.01, The three dimensional sound field reproduction systems can be categorized mainly into two types, physical reproduction, and artistic reproduction. The former is sometimes referred to as scientific or engineering, and the latter is sometimes recognized as psychological reproduction using phantom images produced by, for example, amplitude panning and the other effects. The purpose of the reproduction system is widely spread. The system can be a design tool of enclosed space, such as a concert hall, before practical construction by reproducing physical characteristics accurately. Also, the system can be a pure entertainment tool, mostly with visual images. Of course, the scale and necessary conditions vary with their purpose and objectives; however, it might be interesting to investigate what are the essential factors for the higher total performance of reproduction systems. We currently hypothesize that the following four conditions might be necessary for the total performance of the versatile sound field reproduction system. A) physical accuracy, B) robustness against disturbance, C) flexibility for additional direction, D) capability of integration with visual stimuli. As a platform of examination, 24-channel narrow directional microphone array and 24-channel loudspeaker array are used. The boundary surface control principle and its modified version are adopted for the physical background. As examples, several practical efforts are attempted to assure the total performance of the system effectively..
4.	Hiroshi Kashiwazak, Akira Omoto, Sound field reproduction system using narrow directivity microphones and boundary surface control principle, Acoustical Science and Technology, 10.1250/ast.36.1, 39, 4, 2018.07, Boundary surface control (BoSC) is a useful method of reproducing the sound field physically. However, it is challenging in the case of real-time operation. This is mainly due to the calculation cost of a lot of inverse filter convolutions to obtain reproduction signals. This paper proposes a method for reducing of number of inverse filters and implements it in 24-channel narrow directivity (shotgun) microphone array and 24-channel circularly arranged loudspeaker array. Moreover, it provides an experimental evaluation of the reproduction accuracy according to measurement of reproduced wavefront. The accuracy of the reproduced wavefront by the filters, whose number was reduced to less than 1/5 by proposed method, was comparable with the case of full number of filters. Finally, a system aiming at sound field reproduction in a wide frequency range was constructed by a hybrid method of reproducing with an inverse filter in the low range and directly outputting from the speaker in the direction corresponding to the microphone in the high frequency range. We confirmed that real-time processing is possible for this hybrid method by using a convolution plug-in of digital audio workstation software..
5.	Akira Omoto, Shiro Ise, Yusuke Ikeda, Kanako Ueno, Seigo Enomoto, Maori Kobayashi, Sound field reproduction and sharing system based on the boundary surface control principle , Acoustical Science and Technology, 10.1250/ast.36.1, 36, 1, 1-11, 2015.01.
6.	Akira Omoto, Comment on 'A theoretical framework for quantitatively characterizing sound field diffusion based on scattering and absorption coefficient of walls', Journal of the Acoustical Society of America, 10.1121/1.4768884, 133, 1, 9-12, 2013.01.
7.	Yuki Matsumoto, Akira Omoto, Application of an Auditory Filter for the Evaluation of Sounds and Sound Fields, Building Acoustics, 10.1260/1351-010X.18.1-2.175, 18, 1-2, 175-188, ISRAでのポスター発表原稿が掲載されたもの, 2011.03.
8.	Yuki Matsumoto, Akira Omoto, Sound Field Evaluation by Using Auditory Filter: Application of Dynamic Compressive Gammachirp Filter, Acoustical Science and Technology, 31, 5, 368-370, 2010.09.
9.	Taeko Akama, Hisaharu Suzuki, Akira Omoto, Distribution of selected monaural acoustical parameters in concert halls, Applied Acoustics, 10.1016/j.apacoust.2010.01.004, 71, 6, 564-577, Vol. 28, pp.84-89, 2010.06.
10.	Yasuhiko Nagatomo, Namiko Hiramatsu, Genta Yamauchi, Akira Omoto, Variable reflection acoustic wall system by active sound radiation, Acoustical Science and Technology, Vol. 28, pp.84-89, 2007.03.
11.	Hisaharu Suzuki, Akira Omoto, Kyoji Fujiwara, Treatment of boundary condition by finite difference time domain method, Acoustical Science and Technology, Vol. 28, pp.16-26, 2007.01.
12.	Yoshinari Fukushima, Hisaharu Suzuki, Akira Omoto, Visualization of reflected sound in enclosed space by sound intensity measurement, Acoustical Science and Technology, Vol. 27, pp.187-189, 2006.05.
13.	Yoko Takenouchi, Hisaharu Suzuki, Akira Omoto, Behavior of the practically implemented filtered reference LMS algorithm in an active noise control system, Acoustical Science and Technology, Vol. 27, pp.20-27, 2006.01.
14.	Masataka Nakahara, Akira Omoto, Kyoji Fujiwara, The effect of a mixing console on the monitoring response in a mixing room, Acoustical Science and Technology, Vol. 26, pp.90-101, 2005.03.
15.	Akira Omoto, Active Noise Control: Adaptive Signal Processing and Algorithm, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E85-A, No. 3 pp. 548-557, 2002.03.
16.	Akira Omoto, Daisuke Morie, Kyoji Fujiwara, Behavior of adaptive algorithms in active noise control systems with moving noise sources, Acoustical Science and Technology, Vol. 23, No. 2 pp. 84-89, 2002.03.
17.	Gensei Matsumoto, Kyoji Fujiwara, Akira Omoto, A study on the insertion loss of a noise barrier for a directional sound source, The Journal of the Acoustical Society of Japan (E), Vol. 20, No. 4, pp. 325-328, 1999.07.
18.	Akira Omoto, S. J. Elliott, The Effect of Structured Uncertainty in the Acoustic Plant on Multichannel Feedforward Control Sysrtems, IEEE Transaction on Speech and Audio Processing, Vol. 7, No. 2, pp. 204-212, 1999.03.
19.	Akira Omoto, Tohru Matsui, Kyoji Fujiwara, The behaviour of an adaptive algorithm with a moving primary source, The Journal of the Acoustical Society of Japan (E), Vol. 19, No. 3, pp. 211-221, 1998.05.
20.	尾本章，S. J. Elliott, The Effect of Structured Uncertainty in Multichannel Feedforward Control Sysrtems, 1996 IEEE International Conference on Acoustics, Speech & Signal Processing, Volume 2, pp. 965-968, 1996.05.
21.	Akira Omoto, Kyoji Fujiwara, A study of an actively controlled noise barrier, Journal of the Acoustical Society of America, Vol. 94, No. 4 pp. 2173-2180, 1993.10.

Presentations

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1.	A study of higher-order Ambisonics encoding using narrow directional microphone array.
2.	Evaluation and Reproduction of the Stage Sound Field Using Directional Characteristics of Sound Source and Directional Impulse Responses.
3.	Performance evaluation of sound field reproduction system using directional impulse responses.
4.	Horizontal localization of 24-channel 3D sound field reproduction system: Comparison and examination by reproduction method.
5.	A Study on Measurement of Sound Absorption Coefficient with Multi-channel Sound Field Reproduction System: Performance Comparison with Various Channel Numbers.
6.	Reproducibility Comparison of Boundary Surface Control and Higher-Oder Ambisonics Using Higher Or- der Spherical Harmonic Spectrum Estimation.
7.	Application of loudness correction considering arrival direction of sound to operation noise of vacuum cleaner.
8.	Auditory vertical perception of 24 channels 3D sound field reproduction system - Comparison between direct sound field reproduction and boundary surface control and incongruity of elevation mismatch between auditory and visual stimulus-.
9.	Acoustic FEM analysis considering difference in sound insulation performance of noise barrier.
10.	Akira Omoto, Hiroshi Kashiwazaki, Performance comparison of various strategies in 24-channel versatile sound field reproduction system, 178th meeting of the Acoustical Society of America, 2019.12, A sound field reproducing system which consists of a hedgehog-shaped 24-channel narrow directional microphone and the speakers of the same number is currently proposed. The system is aimed for the versatile usage, for example, the reproduction of the sound field in a concert hall, and also applicable to various simulation for noise control engineering. The basic reproduction technique is intuitive and straightforward, in which a signal recorded by a particular microphone would be emitted from a loudspeaker located at the almost same direction. To compensate for the insufficient directional characteristics in the low- frequency range, some kinds of signal processing are necessary. So far, several methods, such as the inverse filtering based on the boundary surface control principle, the ambisonics, the beamforming, are attempted. The processed low-frequency components are integrated with the directly assigned high-frequency components. In addition to the procedure that uses 24 recorded signals, the alternative method which reproduces the directional information by convolving the measured directional impulse responses with the signal of the fewer channel, such as monaural or stereo format, could be used. The performance of these various reproduction methods is compared with each other..
11.	Akira Omoto, Tomohiro SHIMIZU, Hiroshi Kashiwazaki, Sound field Reproduction using Convolving Directional Dry Signals and Directional Impulse Responses, International Symposium on Room Acoustics, 2019.09, The overall performance of a loudspeaker-based sound-field reproducing system is examined. We assume it essential to satisfy four conditions. (A) The reproduction is based on physical principles to ensure the fundamental performance. (B) The system is robust against unavoidable disturbances, such as the presence of listeners. (C) There is room to accept additional direction, such as an intentional change in reverberation or frequency characteristics. (D) The system has high affinity with other stimulation, such as visual information. In a practical examination, a 24-channel hedgehog-shaped narrow-directional microphone array and a 24-channel loudspeaker array in which loudspeakers are arranged at intervals of 45° in the azimuth angle and in three layers are used as a platform. Using this system and considering condition (A), the reproduction of the sound field in a concert hall is attempted. The directional impulse responses measured in 24 directions are convoluted with conventional stereo recording signals or signals recorded in different directions to cope with the directivity of musical instruments. The performance is examined in terms of the reproducibility of physical parameters and subjective evaluation..
12.	Hiroshi Kashiwazaki, Akira Omoto, Attempt to improve the total performance of sound field reproduction system: Integration of wave-based methods and simple reproduction method, International Congress on Acoustics, 2019.09, The sound field reproduction system can be applied to various applications. The primary objective of the sys- tem is to physically reproduce an arbitrary sound field correctly. However, physical accuracy is not the only requirement in a situation where the system is actually used. Through several applications, we assumed the following four factors as total performance; A) physical accuracy, B) robustness against disturbances, C) flexi- bility for additional direction, and D) capability of integration with visual media. We used 24-channel narrow directional microphone array and 24-channel loudspeaker as a platform to be considered and worked to improve overall performance. As one of the reproduction methods, directional information can be easily reproduced by amplitude panning which relies on the directivity of the microphone themselves, but the microphone leakage effect occurs in the low frequency. On the other hand, wave-based methods such as boundary surface control or higher-order ambisonics are effective for physical accuracy, but control of high frequency is difficult. There- fore, if wave-based method and simple reproduction method are combined, there is a possibility to reproduce a wide frequency range well. We discuss the total performance of this reproduction method through ITD/ILD measurement and visualization of a wide range of wavefront..
13.	Application of a 3D sampling reverberator for sound post-production works.
14.	Proposal and application of sound field reproduction system using directional impulse responses.
15.	Performance improvement of sound field reproduction system using narrow directional microphone array – Attempt of Higher-Order Ambisonics control in low frequency –.
16.	Auditory distance perception of 24 channels 3D sound field reproduction system - Comparison between direct sound field reproduction and boundary surface control and incongruity of distance mismatch between auditory and visual stimulus -.
17.	On factors contributing to high presence in the multi-channel sound field reproduction system.
18.	Detection of Applause from a Sound Field for Ambient Transmission in an Oral Presentation Live Viewing System.
19.	Introducing 360 degrees Video on Cylindrical Screen to Sound Field Reproduction System - System Construction and Subjective Localization Tests -.
20.	Correction of frequency characteristics of simple sound field reproduction system using narrow directional microphone array.
21.	Development of a 3D sampling reverberator for sound post-production works.
22.	FEM Approach to Exterior Helmholtz Problem using Infinite Element for Noise Reduction Estimation of Railway Noise Barrier.
23.	Local inverse analysis for boundary surface control using l_1-regularization.
24.	Variation of Loudness by Sound Source Distribution.
25.	The evaluation of APRICOT system for high-realistic live viewing.
26.	Development of a 3D sampling reverberator generated by measured sound intensities.
27.	Immersive audio and architectural acoustics.
28.	Determination Method of Regularization Parameter in Inverse Filter Matrix for Sound Field Reproduction - Introduction of Morozov's Discrepancy Principle-.
29.	Reduction of number of inverse filters on boundary surface control.
30.	Noise Reduction Estimation for Noise Barrier on Railway Viaduct using FEM Acoustic Analysis.
31.	Evaluation examples of reproduced sound fields by sound intensity measurements.
32.	Physical evaluation of reproduced sound field by sound intensity measurement and/or analysis.
33.	Pilot study of applause detection for applause and handclap feedback on live viewing.
34.	The evaluation of guessing number of applauding people for applause sound synthesis.
35.	Extraction of Applause from a Sound Field for Ambient Transmission in a Live Viewing System.
36.	Comparison and investigation of sound field isotropy with various measurement systems.
37.	The evaluation of sound field isotropy by using hedgehog microphone array.
38.	Variation of Loudness considering the Arrival Direction of Sound.
39.	Development of an algorithm for extracting sound source information from measured sound intensities and visualizing method of them.
40.	尾本章, Sound field reproduction system with active reverberation, The 5th joint meeting of the Acoustical Society of America and the Acoustical Society of Japan, 2016.12.
41.	Evaluation of random incidence sound absorption coefficient with multi-channel sound reproduction system.
42.	Development of the VSV4, a support tool for acoustic design work by measuring, analyzing and 3D-visualizing sound intensities.
43.	Performance Improvements of Sound Reproduction System with Boundary Surface Control Principle.
44.	Performance Improvement of 3D Sound Field Reproduction System.
45.	Study on the evaluation of moving sound source localization for 3-D sound field reproduction systems -Comparison of MUSIC and Particle filter.
46.	Pilot study of applause sound generator depending on the listening environment.
47.	Realization of random incidence to acoustic material in small sized enclosure -Control of directional characteristics of sound propagation by active impedance control-.
48.	Measurement, evaluation and control of sound field.
49.	Relationship between values of physical evaluations for room acoustics and subjective impressions for three dimensional sound field reproduction system.
50.	Basic study for realization of an active reverberation box. - Effect of location and dimension of sound sources on the generated sound field -.
51.	An example of a design strategy by using a modal summation method for controlling low frequency properties of an audio playback environment.
52.	The extra value of a 3-D sound field reproduction -Comparison between general listeners and acousticians-.
53.	Study on the evaluation of moving sound source localization for 3-D sound field reproduction systems.
54.	Sound field capturing device with super cardioid microphone arrays: Construction of simple sound field reproducing system with loudspeaker array.
55.	Akira Omoto, Takahiro Nishiyama, Yuki Yoshimura, Music Performance with Variable Reflection Acoustic Wall System, Forum Acusticum, 2014.09.
56.	The effects of diffuser on sound filed.
57.	A effect of diffuser’s setting on the enclosed sound field: Foucus on direction distribution of reflected sound.
58.	Study on application of active control in the enclosed sound field-Implementation of virtual error sensor by pre-measurement impulse response-.
59.	Modeling of porous material for Finite difference time domain method.
60.	Selection of receiving positions suitable for evaluating acoustical parameters.
61.	Fundamental Study of Active Impedance Control.
62.	Study on characteristic of various microphone arrangements for surround recording.
63.	Basic study on the sound field control in rooms by using virtual microphone.
64.	Effect of variable reflection acoustic wall system on sound field.
65.	Study of active reverberation box: Design of adaptive controller.
66.	Selection of receiving positions suitable for evaluating acoustical parameters.
67.	Acoustic material of variable reflection by sound radiation.
68.	Selection of receiving positions suitable for evaluating acoustical parameters.
69.	Introduction of Auditory Filter into Evaluation of Characteristics of Small Enclosures.
70.	Evaluation method of sound fields in enclosures using sound intensity: Comparison of various methods for image source detection.
71.	The performace of Active Reverberation Box by numerical simulation.

Educational Activities

Undergraduate Program
Theoretical Acoustics, Lecture and Semminar: basics of the physical acoustics, e.g., derivation of the wave equation, fundamental solution, sound source, and so on.
Room Acoustics: basics of the architectural acoustics, e.g., geometrical acoustics, statistical acoustics, wave acoustics.
Rating and Control of Noise: Regulation of noise, control methodology, acoustical material.
Nonlinear Vibration: basics of nonlinear acoustics.

Graduate Program
Acoustic Environment Control: Pronciples and applications of active control, the behavior of the adaptive algorithms used in the control.
Cultural Hall Management Engineer Training Program: Representative, and Concert Hall Acoustics.

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https://kyushu-u.pure.elsevier.com/en/persons/akira-omoto
　Reseacher Profiling Tool　Kyushu University Pure

http://www.design.kyushu-u.ac.jp/~omotoken/
Home Page of Omoto Lab. .