Kyushu University Academic Staff Educational and Research Activities Database
List of Presentations
Akira Omoto Last modified date:2020.01.03

Professor / Sound Culture, Art Management / Department of Communication Design Science / Faculty of Design

1. A Study on Measurement of Sound Absorption Coefficient with Multi-channel Sound Field Reproduction System: Performance Comparison with Various Channel Numbers.
2. Reproducibility Comparison of Boundary Surface Control and Higher-Oder Ambisonics Using Higher Or- der Spherical Harmonic Spectrum Estimation.
3. Application of loudness correction considering arrival direction of sound to operation noise of vacuum cleaner.
4. 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-.
5. Acoustic FEM analysis considering difference in sound insulation performance of noise barrier.
6. 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..
7. 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..
8. 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..
9. Application of a 3D sampling reverberator for sound post-production works.
10. Proposal and application of sound field reproduction system using directional impulse responses.
11. Performance improvement of sound field reproduction system using narrow directional microphone array – Attempt of Higher-Order Ambisonics control in low frequency –.
12. 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 -.
13. On factors contributing to high presence in the multi-channel sound field reproduction system.
14. Detection of Applause from a Sound Field for Ambient Transmission in an Oral Presentation Live Viewing System.
15. Introducing 360 degrees Video on Cylindrical Screen to Sound Field Reproduction System - System Construction and Subjective Localization Tests -.
16. Correction of frequency characteristics of simple sound field reproduction system using narrow directional microphone array.
17. Development of a 3D sampling reverberator for sound post-production works.
18. FEM Approach to Exterior Helmholtz Problem using Infinite Element for Noise Reduction Estimation of Railway Noise Barrier.
19. Local inverse analysis for boundary surface control using l_1-regularization.
20. Variation of Loudness by Sound Source Distribution.
21. The evaluation of APRICOT system for high-realistic live viewing.
22. Development of a 3D sampling reverberator generated by measured sound intensities.
23. Immersive audio and architectural acoustics.
24. Determination Method of Regularization Parameter in Inverse Filter Matrix for Sound Field Reproduction - Introduction of Morozov's Discrepancy Principle-.
25. Masataka Nakahara, Akira Omoto, Yasuhiko Nagatomo, Development of a 4-pi sampling reverberator, VSVerb. - Source reduction, 145th Audio Engineering Society International Convention, AES 2018, 2018.01, The authors developed a 4-pi sampling reverberator, named VSVerb, which restores a 4-pi reverberant field by using information of dominant reflections which are captured in a target space. The timings and amplitudes of reflections are obtained from the analyses results of the sound intensities which are measured at the site in orthogonal three directions. The generated reverberation provides high S/N performance and enables to adjust various acoustic parameters with no additional measurements. These advantages provide the VSVerb with high affinity with post-production works. In order to enhance its affinity with object-based production schemes, this manuscript proposes a practical method to reduce a number of reflections from generated reverberations. The method, called Source Reduction, thins out reflections with less auditory deterioration..
26. Daigo Sato, Masakazu Kiyama, Takefumi Kozasa, Akira Omoto, Practical use of an additional noise barrier for high speed train, 47th International Congress and Exposition on Noise Control Engineering: Impact of Noise Control Engineering, INTER-NOISE 2018, 2018.01, Additional noise barriers made of transparent polycarbonate are installed on the existing concrete noise barriers to improve noise reduction effect for the high speed train. The height of the additional noise barriers are limited with due consideration on structural strength of the viaduct. The higher the additional noise barriers installed are, the larger the wind load acting on the viaduct is. Therefore, it is inevitable to reinforce the viaduct sufficiently for raising the height of noise barriers than ever before. The authors have proposed a novel noise barrier which can reduce the wind load by swing mechanism. In a strong wind condition, a part of the noise barrier opens to reduce the burden to the viaduct, while it keeps closing to work as a noise barrier in an ordinary wind condition. In this study, sound reduction index of the proposed noise barrier was measured by sound intensity method. The swing mechanical structure was examined by wind tunnel tests and a field test. As a result, it was confirmed that the noise insulation performance was sufficient and the swing mechanism was efficient in reducing a wind load acting on a viaduct..
27. Akira Omoto, Hiroshi Kashiwazaki, Sound field acquiring and reproducing system for auditorium acoustics, 47th International Congress and Exposition on Noise Control Engineering: Impact of Noise Control Engineering, INTER-NOISE 2018, 2018.01, Sound field reproduction systems are useful item for auditorium acoustics. The system can be used for comparison of several fields, for auralization of design concept, and might be useful for archiving historical fields and so on. The acquiring and reproducing methods in the system can be roughly divided by their basic concept into two categories; aiming to reproduce wave field precisely and aiming to create phantom sound image and intended sound field by aesthetic method. This research focuses on moderate integration of both methods for reproducing sound field of auditorium..
28. Reduction of number of inverse filters on boundary surface control.
29. Noise Reduction Estimation for Noise Barrier on Railway Viaduct using FEM Acoustic Analysis.
30. Evaluation examples of reproduced sound fields by sound intensity measurements.
31. Physical evaluation of reproduced sound field by sound intensity measurement and/or analysis.
32. Pilot study of applause detection for applause and handclap feedback on live viewing.
33. The evaluation of guessing number of applauding people for applause sound synthesis.
34. Extraction of Applause from a Sound Field for Ambient Transmission in a Live Viewing System.
35. Comparison and investigation of sound field isotropy with various measurement systems.
36. The evaluation of sound field isotropy by using hedgehog microphone array.
37. Variation of Loudness considering the Arrival Direction of Sound.
38. Development of an algorithm for extracting sound source information from measured sound intensities and visualizing method of them.
39. Masataka Nakahara, Akira Omoto, Yasuhiko Nagatomo, A simple evaluating method of a reproduced sound field by a measurement of sound intensities using Virtual Source Visualizer, 143rd Audio Engineering Society Convention 2017, AES 2017, 2017.01, Recently, many kinds of technologies for restoring/reproducing 3D sound fields are proposed. However, it is little opportunity to compare these acoustic performances under a common condition. Though a subjective evaluation is one of the most effective methods for evaluating reproduced sound fields, it requires careful effort. Therefore, the authors propose an alternative method which requires only a physical measurement of sound intensities. Because the method is based on the intensity analysis, “sound images” are assumed to be “amplitude-based phantom sound sources” here. In order to verify effectiveness of the method, various types of reproduced fields were measured and analyzed. As a result, it is ascertained that the method can evaluate proper features of reproduced sound fields, regardless of their restoring techniques..
40. Kosuke Goto, Akira Omoto, Evaluation of sound absorption characteristics of material with multichannel sound field reproduction system, 46th International Congress and Exposition on Noise Control Engineering: Taming Noise and Moving Quiet, INTER-NOISE 2017, 2017.01, Multi-channel sound field reproduction system is utilized as a measurement system of absorption characteristics of acoustical material. The used system named "Sound Cask" has ninety-six channel evenly distributed loudspeakers in around 8 m3 enclosure and works with boundary surface control principle that reproduce any sound field by replicating the pressure distribution at the surface of arbitrary enclosed region. The reproduced field in Sound Cask is around 0.4 m diameter sphere inside the Cask. The random incidence condition is aimed in this study. Uncorrelated noises that are processed with inverse filter matrix are used as measurement signal. This condition is thus equivalent that the acoustical material is exposed to uncorrelated noises coming from various directions without undesired effect of the enclosure. First, the degree of isotropy in the reproduced field is measured by the index called UAD, uniformity of arrival directions, that evaluates the uniformity of directions of sound intensities. The results indicate the superiority of proposed method with inverse filter compared with conventional reverberation chamber especially at low frequency. The absorption coefficients of small sized fiber glass (e.g., 0.3 × 0.3 m2) are then measured by in-situ two microphones method. The results show reasonable values compared with typical coefficients obtained by conventional measurement method. These indicate effectiveness and possibility of proposed method. Additionally, the proposed method can reproduce any desired conditions of sound incidence to the material such as oblique and simultaneous incidence from plural directions. Stable measurement with such specialized conditions would be expected with proposed method..
41. Takashi Mikami, Masataka Nakahara, Akira Omoto, Physical evaluations of reproduced sound fields by measurements of sound intensities using Virtual Source Visualizer, 143rd Audio Engineering Society Convention 2017, AES 2017, 2017.01, In order to evaluate acoustic properties of reproduced sound fields, sound intensities were measured and analyzed in various types of multichannel studios by using a Virtual Source Visualizer (VSV hereafter). First, two different methods to reproduce sound fields are examined; 24ch amplitude-based phantom sound sources and Kirchhoff-Helmholtz-integral-based Boundary Surface Control principle. Secondly, sound fields created by four different types of 3D panners are examined; Dolby Atmos, DTS:X, Auro-3D and 22.2ch. Through these measurements, it was demonstrated that the VSV analyzes acoustic features of reproduced fields well, and interchangeabilities and differences of acoustic properties among different reproduced fields can be understood clearly. The session discusses accuracy and features of various types of reproduced sound fields which we measured and analyzed by the VSV..
42. 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.
43. Evaluation of random incidence sound absorption coefficient with multi-channel sound reproduction system.
44. Development of the VSV4, a support tool for acoustic design work by measuring, analyzing and 3D-visualizing sound intensities.
45. Performance Improvements of Sound Reproduction System with Boundary Surface Control Principle.
46. Performance Improvement of 3D Sound Field Reproduction System.
47. Study on the evaluation of moving sound source localization for 3-D sound field reproduction systems -Comparison of MUSIC and Particle filter.
48. Pilot study of applause sound generator depending on the listening environment.
49. Realization of random incidence to acoustic material in small sized enclosure -Control of directional characteristics of sound propagation by active impedance control-.
50. Measurement, evaluation and control of sound field.
51. Relationship between values of physical evaluations for room acoustics and subjective impressions for three dimensional sound field reproduction system.
52. Basic study for realization of an active reverberation box. - Effect of location and dimension of sound sources on the generated sound field -.
53. An example of a design strategy by using a modal summation method for controlling low frequency properties of an audio playback environment.
54. The extra value of a 3-D sound field reproduction -Comparison between general listeners and acousticians-.
55. Study on the evaluation of moving sound source localization for 3-D sound field reproduction systems.
56. Sound field capturing device with super cardioid microphone arrays: Construction of simple sound field reproducing system with loudspeaker array.
57. Akira Omoto, Takahiro Nishiyama, Yuki Yoshimura, Music Performance with Variable Reflection Acoustic Wall System, Forum Acusticum, 2014.09.
58. The effects of diffuser on sound filed.
59. A effect of diffuser’s setting on the enclosed sound field: Foucus on direction distribution of reflected sound.
60. Study on application of active control in the enclosed sound field-Implementation of virtual error sensor by pre-measurement impulse response-.
61. Modeling of porous material for Finite difference time domain method.
62. Selection of receiving positions suitable for evaluating acoustical parameters.
63. Fundamental Study of Active Impedance Control.
64. Study on characteristic of various microphone arrangements for surround recording.
65. Basic study on the sound field control in rooms by using virtual microphone.
66. Effect of variable reflection acoustic wall system on sound field.
67. Study of active reverberation box: Design of adaptive controller.
68. Selection of receiving positions suitable for evaluating acoustical parameters.
69. Improvement of calculation speed on FDTD: Effect of SIMD parallelization.
70. Basic research on evaluation of room acoustic characteristics by using auditory filter.
71. Selection of receiving points suitable for evaluating acoustical parameters.
72. Estimating methods of sound arriving direction in rooms.
73. The performance of active reverberation box.
74. Variable Reflection Acoustic Wall System by Active Sound Radiation.
75. Acoustic material of variable reflection by sound radiation.
76. Selection of receiving positions suitable for evaluating acoustical parameters.
77. Introduction of Auditory Filter into Evaluation of Characteristics of Small Enclosures.
78. Evaluation method of sound fields in enclosures using sound intensity: Comparison of various methods for image source detection.
79. The performace of Active Reverberation Box by numerical simulation.
80. Visualization of structure of reflection sounds using instantaneous intensity.
81. Basic Consideration of Active Reverberation Box.
82. Consideration of Measurement Technic for Oblique Incidence Absorption Coefficient.
83. Acoustic material of variable Reflection coefficient by sound radiation.
84. The acoustical effect of a mixing console and its reduction in a monitoring response.
85. Visualization ofreflections in small enclosures.
86. Acoustic material of variable reflection coefficient by sound radiation.
87. Active control of low frequency acoustic energy in enclosures.
88. The effect of equipment and furniture on acoustical properties of a control room.