著者
Shoichi Koyama
出版者
ACOUSTICAL SOCIETY OF JAPAN
雑誌
Acoustical Science and Technology (ISSN:13463969)
巻号頁・発行日
vol.41, no.1, pp.269-275, 2020-01-01 (Released:2020-01-06)
参考文献数
33
被引用文献数
5

Estimating and interpolating a sound field from measurements using multiple microphones are fundamental tasks in sound field analysis for sound field reconstruction. The sound field reconstruction inside a source-free region is achieved by decomposing the sound field into plane-wave or harmonic functions. When the target region includes sources, it is necessary to impose some assumptions on the sources. Recently, it has been increasingly popular to apply sparse representation algorithms to various sound field analysis methods. In this paper, we present an overview of sparsity-based sound field reconstruction methods and also demonstrate their application to sound field recording and reproduction.
著者
Katsuhiko Yamamoto Toshio Irino Toshie Matsui Shoko Araki Keisuke Kinoshita Tomohiro Nakatani
出版者
ACOUSTICAL SOCIETY OF JAPAN
雑誌
Acoustical Science and Technology (ISSN:13463969)
巻号頁・発行日
vol.40, no.2, pp.84-92, 2019-03-01 (Released:2019-03-01)
参考文献数
27
被引用文献数
2

The speech-based envelope power spectrum model (sEPSM) was developed to predict the speech intelligibility of sounds produced by nonlinear speech enhancement algorithms such as spectral subtraction. It is a linear model with a linear, level-independent gammatone (GT) filterbank as the front-end. Therefore, it seems difficult to evaluate speech sounds with low and high sound pressure levels (SPLs) consistently because the intelligibility of the speech is dependent on the SPL as well as the signal-to-noise ratio. In this study, the sEPSM was extended with the dynamic compressive gammachirp (dcGC) auditory filterbank and a ``common'' normalization factor of the modulation power spectrum component to improve the predictability of the model. For evaluating the proposed model, we performed subjective experiments on the intelligibility of speech sounds enhanced by spectral subtraction and a Wiener filter algorithm. We compared the subjective speech intelligibility scores with the objective scores predicted by the proposed dcGC-sEPSM, original GT-sEPSM, and other well-known conventional methods such as the short-time objective intelligibility measure (STOI), coherence speech intelligibility index (CSII), and hearing aid speech perception index (HASPI). The result shows that the proposed dcGC-sEPSM predicted the subjective results better did than the other methods.
著者
Tatsuhiro Tanaka Makoto Otani
出版者
ACOUSTICAL SOCIETY OF JAPAN
雑誌
Acoustical Science and Technology (ISSN:13463969)
巻号頁・発行日
vol.44, no.4, pp.317-327, 2023-07-01 (Released:2023-07-01)
参考文献数
29

Isotropy is a fundamental property of a diffuse sound field. Although several studies have proposed an isotropy indicator to quantify the extent of the isotropy of a sound field, what is not yet very clear is how to interpret the quantified isotropy using these indicators. This study aims to contribute to the understanding of the isotropy by (i) modifying an existing isotropy indicator based on the spherical harmonic expansion and (ii) presenting isotropic sound field model composed of a finite number of plane waves. Theoretical and numerical investigations show that a limited-degree isotropy can be established by using the isotropy indicator and the isotropic sound field model.
著者
A. J. Patitsas
出版者
ACOUSTICAL SOCIETY OF JAPAN
雑誌
Acoustical Science and Technology (ISSN:13463969)
巻号頁・発行日
vol.43, no.6, pp.297-305, 2022-11-01 (Released:2022-11-01)
参考文献数
27

It is verified that the source of the acoustic emissions when beach sand or other squeaky grains are stepped on or impacted by a pestle lies in a thin shear band directly under the pestle. The grain layers in this band slide one over another at a slow creepy pace giving rise to energy transfer, via the stick-slip effect, from the impacting pestle to the elastic vibrations in the shear bands at the grain contact areas. In turn, this vibration energy feeds the elastic modes of vibration along the vertical grain columns or equivalently, the elastic modes of vibration in the shear band under the pestle comprising the vibrating columns, with dominant frequency in the range of 1,000 Hz. In search of an explanation of the acoustic emissions when booming dune sand is pushed by a blade or is freely avalanching, we adopt the concept of the collision shear band, where, due to the high degree of fluidity of the sand mass, the grain layers slide one over another at a brisk pace so that the average collision frequency between grains in two adjacent grain layers defines the dominant frequency of the acoustic emission in the range of 100 Hz.
著者
César D. Salvador Shuichi Sakamoto Jorge Treviño Yôiti Suzuki
出版者
ACOUSTICAL SOCIETY OF JAPAN
雑誌
Acoustical Science and Technology (ISSN:13463969)
巻号頁・発行日
vol.38, no.1, pp.1-13, 2017-01-01 (Released:2017-01-01)
参考文献数
26
被引用文献数
3 5

This paper derives a continuous-space model to describe variations in magnitude of complex head-related transfer functions (HRTFs) along angles and radial distances throughout the horizontal plane. The radial part of this model defines a set of horizontal-plane distance-varying filters (HP-DVFs) that are used to synthesize the HRTFs for arbitrary sound source positions on the horizontal plane from initial HRTFs obtained for positions on a circular boundary at a single distance from the head of a listener. The HP-DVFs are formulated in terms of horizontal-plane solutions to the three-dimensional acoustic wave equation, which are derived by assuming invariance along elevation angles in spherical coordinates. This prevents the free-field inaccurate distance decay observed when assuming invariance along height in cylindrical coordinates. Furthermore, discontinuities along the axis connecting the ears are also overcome, which appear when assuming invariance along the polar angle in interaural coordinates. This paper also presents a magnitude-dependent band-limiting threshold (MBT) for restricting the action of filters to a limited angular bandwidth, which is necessary in practice to enable discrete-space models that consider a finite number of sources distributed on the initial circle. Numerical experiments using a model of a human head show that the overall synthesis accuracy achieved with the proposed MBT outperforms the one achieved with the existing frequency-dependent threshold, especially at low frequencies and close distances to the head.
著者
Atsuto Inoue Yusuke Ikeda Kohei Yatabe Yasuhiro Oikawa
出版者
ACOUSTICAL SOCIETY OF JAPAN
雑誌
Acoustical Science and Technology (ISSN:13463969)
巻号頁・発行日
vol.40, no.1, pp.1-11, 2019-01-01 (Released:2019-01-01)
参考文献数
28
被引用文献数
2 17

For the visualization of a sound field, a widely used method is the superimposition of the sound information onto a camera view. Although it effectively enables the understanding the relationship between space and sound, a planar display cannot resolve depth information in a straightforward manner. In contrast, a see-through head-mounted display (STHMD) is capable of representing three-dimensional (3D) vision and natural augmented reality (AR) or mixed reality (MR). In this paper, we propose a system for the measurement and visualization of a sound field with an STHMD. We created two visualization systems using different types of STHMDs and technologies for realizing AR/MR and a measurement system for a 3D sound intensity map, which can be used together with the visualization system. Through three visualization experiments, we empirically found that the stereoscopic viewing and the convenient viewpoint movement associated with the STHMD enables understanding of the sound field in a short time.
著者
Masayuki Nishiguchi
出版者
ACOUSTICAL SOCIETY OF JAPAN
雑誌
Acoustical Science and Technology (ISSN:13463969)
巻号頁・発行日
vol.27, no.6, pp.375-383, 2006 (Released:2006-11-01)
参考文献数
19

A coding algorithm for speech called harmonic vector excitation coding (HVXC) has been developed that encodes speech at very low bit rates (2.0–4.0 kbit/s). It breaks speech signals down into two types of segments: voiced segments, for which a parametric representation of harmonic spectral magnitudes of LPC residual signals is used; and unvoiced segments, for which the CELP coding algorithm is used. This combination provides near toll-quality speech at 4.0 kbit/s, and communication-quality speech at 2.0 kbit/s, thus outperforming FS1016 4.8-kbit/s CELP. This paper discusses the encoder and decoder algorithms for HVXC, including fast harmonic synthesis, time scale modification, and pitch-change decoding. Due to its high coding efficiency and new functionality, HVXC has been adopted as the ISO/IEC International Standard for MPEG-4 audio.
著者
Stefan Bilbao Michele Ducceschi
出版者
ACOUSTICAL SOCIETY OF JAPAN
雑誌
Acoustical Science and Technology (ISSN:13463969)
巻号頁・発行日
vol.44, no.3, pp.194-209, 2023-05-01 (Released:2023-05-01)
参考文献数
100

Musical string vibration has been the subject of scientific study for centuries. Recent increases in computational power have allowed the exploration of increasingly detailed features of perceptual significance through simulation approaches. The starting point for any simulation is a well-defined model, usually framed as a system of differential equations, with parameters determined by measurement and experiment. This review article is intended to take the reader through models of string vibration progressively, beginning with well-known and well-studied linear models, and then introducing new features that form the basis for the modern study of realistic musical string vibration. These include, first, nonlinear excitation mechanisms, such as the hammer-string and bow-string interaction, and then the collision mechanism, both for pointwise obstructions and over a distributed region. Finally, the linear model of string vibration is generalized to include geometric nonlinear effects, leading to typical nonlinear behaviour such as pitch glides and the appearance of so-called phantom partials due to nonlinear mixing of modes. The article concludes with a general overview of numerical simulation techniques for string vibration.
著者
Hironori Takemoto Seiji Adachi Natsuki Toda
出版者
ACOUSTICAL SOCIETY OF JAPAN
雑誌
Acoustical Science and Technology (ISSN:13463969)
巻号頁・発行日
vol.44, no.1, pp.9-16, 2023-01-01 (Released:2023-01-01)
参考文献数
15

The vocal tract can be modeled as an acoustic tube in the low-frequency region because the plane wave propagation is dominant. Further, it can be considered static for a limited short period during running speech, such as vowels. Thus, its acoustic properties have been examined mainly using the transmission line model (TLM), that is, the one-dimensional static model in the frequency domain. In the present paper, we propose a one-dimensional static model in the time domain based on the finite-difference time-domain method. In this model, the vocal tract is represented by the cascaded acoustic tubes of different cross-sectional areas. The pressure and wall vibration effects are simulated at the center of each tube. On the other hand, the volume velocity is calculated at the labial end. According to the leapfrog algorithm, the pressure and volume velocity are sequentially computed. As a result, the impulse responses of the vocal tracts for the five Japanese vowels were calculated, and the corresponding transfer functions agreed well with those calculated by the TLM in the low-frequency region. The mean absolute percentage difference of the lower four peaks for the five vowels was 2.3%.
著者
Jungsoon Kim Moojoon Kim
出版者
ACOUSTICAL SOCIETY OF JAPAN
雑誌
Acoustical Science and Technology (ISSN:13463969)
巻号頁・発行日
vol.44, no.1, pp.1-8, 2023-01-01 (Released:2023-01-01)
参考文献数
25

The vibration mode of a bolt-clamped ultrasonic transducer was experimentally analyzed. In the experiment, a designed and manufactured semicircular wedge-shaped jig was used to apply constant pressure to a narrow band-shaped area on the lateral side of the transducer. Constant force was applied to the jig with a vise and a torque wrench. As the position of the pressure applied by the jig moved along the length of the transducer, the change of the input admittance characteristic of the transducer was observed. Each vibration mode was analyzed from the change in the magnitude and the resonant frequency of the input admittance. The proposed method made it possible to practically determine the position of the node for each vibration mode, and is expected to provide useful information to utilize the harmonic modes.