Name

YATABE, Kohei

Official Title

Assistant Professor(without tenure)

Affiliation

(School of Fundamental Science and Engineering)

Sub-affiliation

Affiliated Institutes

波動場・コミュニケーション科学研究所

研究所員 2017-

Educational background・Degree

Educational background

2008/04 -2012/03 Waseda University School of Fundamental Science and Engineering Department of Intermedia Art and Science
2012/04 -2014/03 Waseda University Graduate School of Fundamental Science and Engineering Department of Intermedia Art and Science
2014/04 -2017/03 Waseda University Graduate School of Fundamental Science and Engineering Department of Intermedia Art and Science

Degree

Doctor of Engineering Waseda University

Career

2015/04-2017/03Japan Society for the Promotion of Science (JSPS)Research Fellowships for Young Scientists
2017/04-2018/03Waseda UniversityDepartment of Intermedia Art and ScienceAssistant Professor
2018/04-Waseda UniversityDepartment of Intermedia Art and ScienceAssistant Professor

OfficerCareer(Outside the campus)

2013/04-2019/03The Acoustical Society of Japan (ASJ)ASJ Student & Young Researchers Forum
2018/05-The Institute of Electronics, Information and Communication Engineers (IEICE)IEICE Technical Group on Signal Processing

Award

13th Itakura Prize Innovative Young Researcher Award

2018/03Conferment Institution:Acoustical Society of Japan

Waseda Teaching Award

2018/02Conferment Institution:Waseda University

38th Awaya Prize Young Researcher Award

2015/09Conferment Institution:Acoustical Society of Japan

Best Student Presentation Award

2014/03Conferment Institution:Acoustical Society of Japan

Research Field

Keywords

Acoustics, Optical Metrology, Signal Processing

Grants-in-Aid for Scientific Research classification

Informatics / Human informatics / Perceptual information processing

Engineering / Mechanical engineering / Dynamics/Control

Engineering / Electrical and electronic engineering / Measurement engineering

Paper

Time-frequency-masking-based determined BSS with application to sparse IVA

Yatabe, Kohei; Kitamura, Daichi

ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings Peer Review Yes p.715 - 7192019/05-2019/05

DOI

Detail

Outline:Most of the determined blind source separation (BSS) algorithms related to the independent component analysis (ICA) were derived from mathematical models of source signals. However, such derivation restricts the application of algorithms to explicitly definable source models, i.e., an implicit model associated with some signal-processing procedure cannot be utilized within such framework. In this paper, we propose an extension of the existing algorithm so that any time-frequency masking method (e.g., those developed in speech enhancement literature) can be incorporated into the determined BSS algorithm. As an application of the proposed algorithm, a sparse extension of the well-known independent vector analysis (IVA) is also proposed for illustrating the potentiality of the masking-based implicit source model.

Data-driven design of perfect reconstruction filterbank for DNN-based sound source enhancement

Takeuchi, Daiki; Yatabe, Kohei; Koizumi, Yuma; Oikawa, Yasuhiro; Harada, Noboru

ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings Peer Review Yes p.596 - 6002019/05-2019/05

DOI

Detail

Publish Classification:Research paper (international conference proceedings)

Outline:We propose a data-driven design method of perfect-reconstruction filterbank (PRFB) for sound-source enhancement (SSE) based on deep neural network (DNN). DNNs have been used to estimate a time-frequency (T-F) mask in the short-time Fourier transform (STFT) domain. Their training is more stable when a simple cost function as mean-squared error (MSE) is utilized comparing to some advanced cost such as objective sound quality assessments. However, such a simple cost function inherits strong assumptions on the statistics of the target and/or noise which is often not satisfied, and the mismatch of assumption results in degraded performance. In this paper, we propose to design the frequency scale of PRFB from training data so that the assumption on MSE is satisfied. For designing the frequency scale, the warped filterbank frame (WFBF) is considered as PRFB. The frequency characteristic of learned WFBF was in between STFT and the wavelet transform, and its effectiveness was confirmed by comparison with a standard STFT-based DNN whose input feature is compressed into the mel scale.

Deep Griffin–Lim iteration

Masuyama, Yoshiki; Yatabe, Kohei; Koizumi, Yuma; Oikawa, Yasuhiro; Harada, Noboru

ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings Peer Review Yes p.61 - 652019/05-2019/05

DOI

Detail

Publish Classification:Research paper (international conference proceedings)

Outline:This paper presents a novel phase reconstruction method (only from a given amplitude spectrogram) by combining a signal-processing-based approach and a deep neural network (DNN). To retrieve a time-domain signal from its amplitude spectrogram, the corresponding phase is required. One of the popular phase reconstruction methods is the Griffin–Lim algorithm (GLA), which is based on the redundancy of the short-time Fourier transform. However, GLA often involves many iterations and produces low-quality signals owing to the lack of prior knowledge of the target signal. In order to address these issues, in this study, we propose an architecture which stacks a sub-block including two GLA-inspired fixed layers and a DNN. The number of stacked sub-blocks is adjustable, and we can trade the performance and computational load based on requirements of applications. The effectiveness of the proposed method is investigated by reconstructing phases from amplitude spectrograms of speeches.

Phase-aware harmonic/percussive source separation via convex optimization

Masuyama, Yoshiki; Yatabe, Kohei; Oikawa, Yasuhiro

ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings Peer Review Yes p.985 - 9892019/05-2019/05

DOI

Detail

Publish Classification:Research paper (international conference proceedings)

Outline:Decomposition of an audio mixture into harmonic and percussive components, namely harmonic/percussive source separation (HPSS), is a useful pre-processing tool for many audio applications. Popular approaches to HPSS exploit the distinctive source-specific structures of power spectrograms. However, such approaches consider only power spectrograms, and the phase remains intact for resynthesizing the separated signals. In this paper, we propose a phase-aware HPSS method based on the structure of the phase of harmonic components. It is formulated as a convex optimization problem in the time domain, which enables the simultaneous treatment of both amplitude and phase. The numerical experiment validates the effectiveness of the proposed method.

Low-rankness of complex-valued spectrogram and its application to phase-aware audio processing

Masuyama, Yoshiki; Yatabe, Kohei; Oikawa, Yasuhiro

ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings Peer Review Yes p.855 - 8592019/05-2019/05

DOI

Detail

Publish Classification:Research paper (international conference proceedings)

Outline:Low-rankness of amplitude spectrograms has been effectively utilized in audio signal processing methods including non-negative matrix factorization. However, such methods have a fundamental limitation owing to their amplitude-only treatment where the phase of the observed signal is utilized for resynthesizing the estimated signal. In order to address this limitation, we directly treat a complex-valued spectrogram and show a complex-valued spectrogram of a sum of sinusoids can be approximately low-rank by modifying its phase. For evaluating the applicability of the proposed low-rank representation, we further propose a convex prior emphasizing harmonic signals, and it is applied to audio denoising.

Guided-spatio-temporal filtering for extracting sound from optically measured images containing occluding objects

Tanigawa, Risako; Yatabe, Kohei; Oikawa, Yasuhiro

ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings Peer Review Yes p.945 - 9492019/05-2019/05

DOI

Detail

Publish Classification:Research paper (international conference proceedings)

Outline:Recent development of optical interferometry enables us to measure sound without placing any device inside the sound field. In particular, parallel phase-shifting interferometry (PPSI) has realized advanced measurement of refractive index of air. Its novel application investigated very recently is simultaneous visualization of flow and sound, which had been difficult until PPSI enabled high-speed and accurate measurement several years ago. However, for understanding aerodynamic sound, separation of air flow and sound is necessary since they are mixed up in the observed video. In this paper, guided-spatio-temporal filtering is proposed to separate sound from the optically measured images. Guided filtering is combined with a physical-model-based spatio-temporal filterbank for extracting sound-related information without the undesired effect caused by the image boundary or occluding objects. Such image boundary and occluding objects are typical difficulty arose in signal processing of an optically measured sound filed.

Representation of complex spectrogram via phase conversion

Yatabe, Kohei; Masuyama, Yoshiki; Kusano, Tsubasa; Oikawa, Yasuhiro

Acoustical Science and Technology Invitation Yes 40(3) p.170 - 1772019/05-2019/05

DOI

Detail

Publish Classification:Research paper (scientific journal)

Outline:As importance of the phase of complex spectrogram has been recognized widely, many techniques have been proposed for handling it. However, several definitions and terminologies for the same concept can be found in the literature, which has confused beginners. In this paper, two major definitions of the short-time Fourier transform and their phase conventions are summarized to alleviate such complication. A phase-aware signal-processing scheme based on phase conversion is also introduced with a set of executable MATLAB functions (https://doi.org/10/c3qb).

Modal decomposition of musical instrument sounds via optimization-based non-linear filtering

Masuyama, Yoshiki; Kusano, Tsubasa; Yatabe, Kohei; Oikawa, Yasuhiro

Acoustical Science and Technology Peer Review Yes 40(3) p.186 - 1972019/05-2019/05

DOI

Detail

Publish Classification:Research paper (scientific journal)

Outline:For musical instrument sounds containing partials, which are referred to as modes, the decaying processes of the modes significantly affect the timbre of musical instruments and characterize the sounds. However, their accurate decomposition around the onset is not an easy task, especially when the sounds have sharp onsets and contain the non-modal percussive components such as the attack. This is because the sharp onsets of modes comprise peaky but broad spectra, which makes it difficult to get rid of the attack component. In this paper, an optimization-based method of modal decomposition is proposed to overcome it. The proposed method is formulated as a constrained optimization problem to enforce the perfect reconstruction property which is important for accurate decomposition and causality of modes. Three numerical simulations and application to the real piano sounds confirm the performance of the proposed method.

Source directivity approximation for finite-difference time-domain simulation by estimating initial value

Takeuchi, Daiki; Yatabe, Kohei; Oikawa, Yasuhiro

Journal of the Acoustical Society of America Peer Review Yes 145(4) p.2638 - 26492019/04-2019/04

DOIScopus

Detail

Publish Classification:Research paper (scientific journal)

Outline:In order to incorporate a directive sound source into acoustic simulation using the finite-difference time-domain method (FDTD), this paper proposes an optimization-based method to estimate the initial value which approximates a desired directional pattern after propagation. The proposed method explicitly considers a discretized FDTD scheme and optimizes the initial value directly in the time domain so that every effect of the discretization error of FDTD, including numerical dispersion, is taken into account. It is also able to consider a frequency-wise directivity by integrating the Fourier transform into the optimization procedure, even though the estimated result is defined in the time domain. After the optimization, the obtained result can be utilized in any acoustic simulation based on the same FDTD scheme without modification because the result is represented as the initial value to be propagated and no additional procedure is required.

Extracting sound from flow measured by parallel phase-shifting interferometry using spatio-temporal filter

Tanigawa, Risako; Ishikawa, Kenji; Yatabe, Kohei; Oikawa, Yasuhiro; Onuma, Takashi; Niwa, Hayato

Proc. SPIE 10997, Three-Dimensional Imaging, Visualization, and Display 2019 10997p.10997-1 - 10997-62019/04-2019/04

DOI

Detail

Publish Classification:Research paper (international conference proceedings)

Outline:We have proposed a method of simultaneously measuring aerodynamic sound and fluid ow using parallel phase-shifting interferometry (PPSI). PPSI can observe phase of light instantaneously and quantitatively. This method is useful for understanding the aerodynamic sound because PPSI can measure near the source of the aerodynamic sound. However, the components of sound and ow should be separated in order to observe detail near the source of sound inside a region of ow. Therefore, we consider a separation of the component of sound from simultaneously visualized images of sound and ow. In previous research, a spatio-temporal filter was used to extract a component satisfying the wave equation. The ow and the sound are different physical phenomena, and the ow cannot be expressed by the wave equation. Hence, we think that the spatio-temporal filter enables us to separate the component of sound from the simultaneously visualized images. In this paper, we propose a method for separation of ow and sound using spatio-temporal filter in order to visualize the component of the aerodynamic sound near its source. We conducted an experiment of the separation of data measured by PPSI. The results show that the spatio-temporal filter can extract the sound from air-ow except for the sound near objects and boundaries.

Griffin-Lim like phase recovery via alternating direction method of multipliers

Masuyama, Yoshiki; Yatabe, Kohei; Oikawa, Yasuhiro

IEEE Signal Processing Letters Peer Review Yes 26(1) p.184 - 1882019/01-2019/01

DOIScopus

Detail

Publish Classification:Research paper (scientific journal)

Outline:Recovering a signal from its amplitude spectrogram, or phase recovery, exhibits many applications in acoustic signal processing. When only an amplitude spectrogram is available and no explicit information is given for the phases, the Griffin-Lim algorithm (GLA) is one of the most utilized methods for phase recovery. However, GLA often requires many iterations and results in low perceptual quality in some cases. In this letter, we propose two novel algorithms based on GLA and the alternating direction method of multipliers (ADMM) for better recovery with fewer iteration. Some interpretation of the existing methods and their relation to the proposed method are also provided. Evaluations are performed with both objective measure and subjective test.

Visualization system for sound field using see-through head-mounted display

Inoue, Atsuto; Ikeda, Yusuke; Yatabe, Kohei; Oikawa, Yasuhiro

Acoustical Science and Technology Peer Review Yes 40(1) p.12019/01-2019/01

DOIScopus

Detail

Publish Classification:Research paper (scientific journal)

Outline: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.

3D sound source localization based on coherence-adjusted monopole dictionary and modified convex clustering

Tachikawa, Tomoya; Yatabe, Kohei; Oikawa, Yasuhiro

Applied Acoustics Peer Review Yes 139p.267 - 2812018/10-2018/10

DOIScopus

Detail

Publish Classification:Research paper (scientific journal) ISSN:0003682X

Outline:© 2018 Elsevier Ltd In this paper, a sound source localization method for simultaneously estimating both direction-of-arrival (DOA) and distance from the microphone array is proposed. For estimating distance, the off-grid problem must be overcome because the range of distance to be considered is quite broad and even not bounded. The proposed method estimates the positions based on a modified version of the convex clustering method combined with the sparse coefficients estimation. A method for constructing a suitable monopole dictionary based on the coherence is also proposed so that the convex clustering based method can appropriately estimate distance of the sound sources. Numerical and measurement experiments were performed to investigate the performance of the proposed method.

Rectified linear unit can assist Griffin-Lim phase recovery

Yatabe, Kohei; Masuyama, Yoshiki; Oikawa, Yasuhiro

IWAENC, International Workshop on Acoustic Signal Enhancement Peer Review Yes p.555 - 5592018/09-2018/09

DOIScopus

Detail

Publish Classification:Research paper (international conference proceedings)

Outline:Phase recovery is an essential process for reconstructing a time-domain signal from the corresponding spectrogram when its phase is contaminated or unavailable. Recently, a phase recovery method using deep neural network (DNN) was proposed, which interested us because the inverse short-time Fourier transform (inverse STFT) was utilized within the network. This inverse STFT converts a spectrogram into its time-domain counterpart, and then the activation function, leaky rectified linear unit (ReLU), is applied. Such nonlinear operation in time domain resembles the speech enhancement method called the harmonic regeneration noise reduction (HRNR). In HRNR, a time-domain nonlinearity, typically ReLU, is applied for assistance in enhancing the higher-order harmonics. From this point of view, one question arose in our mind: Can time-domain ReLU solely assist phase recovery? Inspired by this curious connection between the recent DNN-based phase recovery method and HRNR in speech enhancement, the ReLU assisted Griffin–Lim algorithm is proposed in this paper to investigate the above question. Through an experiment of speech denoising with the oracle Wiener filter, some positive effect of the time-domain nonlinearity is confirmed in terms of the scores of the short-time objective intelligibility (STOI).

Underdetermined source separation with simultaneous DOA estimation without initial value dependency

Tachikawa, Tomoya; Yatabe, Kohei; Oikawa, Yasuhiro

IWAENC, International Workshop on Acoustic Signal Enhancement Peer Review Yes p.161 - 1652018/09-2018/09

DOIScopus

Detail

Publish Classification:Research paper (international conference proceedings)

Outline:In this paper, a sparsity-based method for solving an underdetermind source separation problem is proposed. The proposed method is formulated as a convex optimization problem with two kinds of sparsity priors: sparsity in time-frequency domain and direction-of-arrival (DOA). These priors enable simultaneous estimation of DOA and sound sources, while the estimation result does not depend on an initialization method thanks to the convexity. Experiments using 4 sound sources recorded by 2 microphones confirmed that every random initial value in the proposed method resulted in the same performance which was better than the conventional methods.

Separating stereo audio mixture having no phase difference by convex clustering and disjointness map

Hiruma, Atsushi; Yatabe, Kohei; Oikawa, Yasuhiro

IWAENC, International Workshop on Acoustic Signal Enhancement Peer Review Yes p.266 - 2702018/09-2018/09

DOIScopus

Detail

Publish Classification:Research paper (international conference proceedings)

Outline:In this paper, a method of constructing binary masks for stereo source separation is proposed. The proposed method consists of two main factors: (1) Disjointness map, and (2) convex directional clustering. The disjointness map quantifies the degree of mixing at each time-frequency bin based on instantaneous frequencies. This map enables to effectively utilize phase information which is usually omitted in stereo music separation. Then, the convex clustering utilizes flexible definitions of adjacency of the time-frequency bins for incorporating more information into directional clustering. Experimental results indicate that the proposed method can obtain a mask closer to the ideal one than the conventional directional clustering.

Model-based phase recovery of spectrograms via optimization on Riemannian manifolds

Masuyama, Yoshiki; Yatabe, Kohei; Oikawa, Yasuhiro

IWAENC, International Workshop on Acoustic Signal Enhancement Peer Review Yes p.126 - 1302018/09-2018/09

DOIScopus

Detail

Publish Classification:Research paper (international conference proceedings)

Outline:In acoustical signal processing, the importance of modifying the phase spectrogram has been shown. Recently, model-based phase recovery which is based on the sinusoidal model has been studied. Although their effectiveness has been proven, some of them deal with the phase in inflexible forms owing to the wrapping effect of phase. In addition, they need much pre-processing, including the estimation of the instantaneous frequency, which is not easy tasks. In order to overcome these issues, we propose a novel model-based phase recovery method which is formulated as an optimization over complex-valued phases. In the proposed method, the instantaneous frequency is not handled fixedly, which avoids the prior estimation of the instantaneous frequency. The technique of optimization on Riemannian manifolds is adopted for efficient computation. The proposed method is validated by noise reduction of audio signals.

Optical visualization of sound field inside transparent cavity using polarization high-speed camera

Ishikawa, Kenji; Yatabe, Kohei; Oikawa, Yasuhiro; Onuma, Takashi; Niwa, Hayato

Proceedings of INTER-NOISE 2018 - 47th International Congress and Exposition on Noise Control Engineering Invitation Yes p.1806-1 - 1806-72018/08-2018/08

Scopus

Detail

Publish Classification:Research paper (international conference proceedings)

Outline:Visualization of a sound field is a powerful tool for understanding acoustic phenomena. Methods using a microphone array such as beamforming and near-field acoustic holography have widely been studied, and these have been applied to industrial problems. As alternative choices for the visualization of the sound field, optical methods have gained a considerable amount of attention due to their capability of non-intrusive measurement. These include laser Doppler vibrometry, Shadowgraphy, Schlieren method, optical digital holography, and parallel phase-shifting interferometry (PPSI). These methods are well developed for the visualization of propagating sound wave in a free field. Also, as these methods can observe the sound field without installing any instruments into the field to be measured, they have the potential to achieve visualization of sound inside a cavity, which is quite important for duct acoustics. This paper presents the single-shot visualization of the sound field inside a transparent cavity using PPSI with a high-speed camera, as well as the brief review of the development of the optical measurement of sound. For the experiments, the sound field inside of a ported speaker box made by acrylic plates was measured. Acoustics resonances and mode patterns inside the box were successively captured.

Measurement of sound pressure inside tube using optical interferometry

Hermawanto, Denny; Ishikawa, Kenji; Yatabe, Kohei; Oikawa, Yasuhiro

Proceedings of INTER-NOISE 2018 - 47th International Congress and Exposition on Noise Control Engineering p.1688-1 - 1688-112018/08-2018/08

Scopus

Detail

Publish Classification:Research paper (international conference proceedings)

Outline:Measurement of sound pressure inside a tube is important for duct acoustics and microphone calibration. Inserting microphone directly into sound field will disturb the field and produce inaccurate measurement result. Recently, non-intrusive sound pressure measurement using optical techniques have been proposed. A laser Doppler vibrometer is used to measure line integrals of sound pressure yield projections and a reconstruction technique is then applied to recover the original sound field from projections. In this paper, measurement of sound pressure distribution using optical method is proposed to realize direct pressure measurement for microphone calibration. A simulation of sound field reconstruction from projections using filtered back-projection technique was developed and the performance was evaluated. The reconstruction performance was evaluated for the projection of plane wave and point source wave of frequency from 1000 Hz to 16000 Hz. The implementation of the proposed method for reconstruction of sound field inside an acrylic tube diameter 61.75 mm, length 22 mm, and thickness 3.5 mm for 1000 Hz sound source from projection using laser Doppler vibrometer was performed. The result shows that the proposed method was able to reconstruct the sound field inside tube and measure pressure distribution.

Optical visualization of sound source of edge tone using parallel phase-shifting interferometry

Tanigawa, Risako; Ishikawa, Kenji; Yatabe, Kohei; Oikawa, Yasuhiro; Onuma, Takashi; Niwa, Hayato

Proceedings of INTER-NOISE 2018 - 47th International Congress and Exposition on Noise Control Engineering p.1494-1 - 1494-92018/08-2018/08

Scopus

Detail

Publish Classification:Research paper (international conference proceedings)

Outline:In order to reduce aerodynamic noise, understanding the nature of aerodynamic sound sources is important. Generally, aerodynamic sound is measured by using microphones. However, microphones should be installed far from aerodynamic sound sources, which makes difficult to understand the nature of aerodynamic sound sources. As non-contact measurement methods, optical measurement methods of sound have been proposed. Among those, parallel phase-shifting interferometry (PPSI) can capture time-varying phenomena. Recently, simultaneous visualization of flow and sound using PPSI has been proposed. This method enables to capture the propagation of sound inside a flow. In this paper, as an application of aerodynamic sound visualization using PPSI, results of visualization of sound sources of edge tones are shown. The nozzle-edge distance and the flow rate, which are parameters of changing frequency of an edge tone, were adjusted from 5 mm to 13 mm at intervals of 1 mm and from 15 L/min to 45 L/min at intervals of 5 L/min, respectively. The frame rate of the high-speed camera in PPSI was set to 20,000 frames per second and the size of the visualization area was 77 mm by 56 mm. From the visualized images, the characteristics of spatial spread of edge tones were observed.

Optical visualization of a fluid flow via the temperature controlling method

Tanigawa, Risako; Ishikawa, Kenji; Yatabe, Kohei; Oikawa, Yasuhiro; Onuma, Takashi; Niwa, Hayato

Optics Letters Peer Review Yes 43(14) p.3273 - 32762018/07-2018/07

DOIScopus

Detail

Publish Classification:Research paper (scientific journal)

Outline:© 2018 Optical Society of America. In this Letter, a visualization method of a fluid flow through temperature control is proposed. The proposed method enables us to visualize an invisible fluid flow by controlling the temperature so that its visibility can be easily adjusted. Such ability of adjusting appearance is effective for visualizing the phenomena consisting of multiple physical processes. In order to verify the validity of the proposed method, the measurement experiment of visualization of both flow and sound in air using parallel phase-shifting interferometry, which is a similar condition to the previous research [Opt. Lett. 43, 991 (2018)], was conducted.

Time-directional filtering of wrapped phase for observing transient phenomena with parallel phase-shifting interferometry

Yatabe, Kohei; Tanigawa, Risako; Ishikawa, Kenji; Oikawa, Yasuhiro

Optics Express Peer Review Yes 26(11) p.13705 - 137202018/05-2018/05

DOIScopus

Detail

Publish Classification:Research paper (scientific journal)

Outline:© 2018 Optical Society of America. Recent development of parallel phase-shifting interferometry (PPSI) enables accurate measurement of time-varying phase maps. By combining a high-speed camera with PPSI, it became possible to observe not only time-varying but also fast phenomena including fluid flow and sound in air. In such observation, one has to remove static phase (time-invariant or slowly-varying phase unrelated to the phenomena of interest) from the observed phase maps. Ordinarily, a signal processing method for eliminating the static phase is utilized after phase unwrapping to avoid the 2π discontinuity which can be a source of error. In this paper, it is shown that such phase unwrapping is not necessary for the high-speed observation, and a time-directional filtering method is proposed for removing the static phase directly from the wrapped phase without performing phase unwrapping. In addition, experimental results of simultaneously visualizing flow and sound with 42 000 fps are shown to illustrate how the time-directional filtering changes the appearance. A MATLAB code is included within the paper (also in https://goo.gl/N4wzdp) for aiding the understanding of the proposed method.

Localization of marine seismic vibrator based on hyperbolic Radon transform

Kusano, Tsubasa; Yatabe, Kohei; Oikawa, Yasuhiro

Acoustical Science and Technology Peer Review Yes 39(3) p.215 - 2252018/05-2018/05

DOIScopus

Detail

Publish Classification:Research paper (scientific journal) ISSN:13463969

Outline:© 2018 The Acoustical Society of Japan. In marine seismic surveys to explore seafloor resources, the structure below the seafloor is estimated from the obtained sound waves, which are emitted by a marine seismic sound source and reflected or refracted between the layers below the seafloor. In order to estimate the structure below the seafloor from returned waves, information of the sound source position and the sound speed are needed. Marine seismic vibrators, which are one of the marine seismic sound sources, have some advantages such as high controllability of the frequency and phase of the sound, and oscillation at a high depth. However, when the sound source position is far from the sea surface, it becomes difficult to specify the exact position. In this paper, we propose a method to estimate the position of a marine seismic vibrator and the sound speed from obtained seismic data by formulating an optimization problem via hyperbolic Radon transform. Numerical simulations confirmed that the proposed method almost achieves theoretical lower bounds for the variances of the estimations.

Determined blind source separation via proximal splitting algorithm

Yatabe, Kohei; Kitamura, Daichi

ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings Peer Review Yes p.776 - 7802018/04-2018/04

DOIScopus

Detail

Publish Classification:Research paper (international conference proceedings)

Outline:The state-of-the-art algorithms of determined blind source separation (BSS) methods based on the independent component analysis (ICA) have gained computational efficiency by the majorization-minimization (MM) principle with a price of losing flexibility. That is, replacing and comparing different source models are not easy in such MM-based framework because it requires efforts to derive a new algorithm each time when one changes the model. In this paper, a general framework for obtaining an ICA-based BSS algorithm is proposed so that a source model can easily be replaced because only a single line of the algorithm must be modified. A sparsity-based extension of the independent vector analysis and a low-rankness-based BSS model using the nuclear norm are also proposed to demonstrate the simplicity and easiness of the proposed framework.

Phase corrected total variation for audio signals

Yatabe, Kohei; Oikawa, Yasuhiro

ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings Peer Review Yes p.656 - 6602018/04-2018/04

DOIScopus

Detail

Publish Classification:Research paper (international conference proceedings)

Outline:In optimization-based signal processing, the so-called prior term models the desired signal, and therefore its design is the key factor to achieve a good performance. For audio signals, the time-directional total variation applied to a spectrogram in combination with phase correction has been proposed recently to model sinusoidal components of the signal. Although it is a promising prior, its applicability might be restricted to some extent because of the mismatch of the assumption to the signal. In this paper, based upon the previously proposed one, an improved prior for audio signals named instantaneous phase corrected total variation (iPCTV) is proposed. It can handle wider range of audio signals owing to the instantaneous phase correction term calculated from the observed signal.

Envelope estimation by tangentially constrained spline

Kusano, Tsubasa; Yatabe, Kohei; Oikawa, Yasuhiro

ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings Peer Review Yes p.4374 - 43782018/04-2018/04

DOIScopus

Detail

Publish Classification:Research paper (international conference proceedings)

Outline:Estimating envelope of a signal has various applications including empirical mode decomposition (EMD) in which the cubic C2-spline based envelope estimation is generally used. While such functional approach can easily control smoothness of an estimated envelope, the so-called undershoot problem often occurs that violates the basic requirement of envelope. In this paper, a tangentially constrained spline with tangential points optimization is proposed for avoiding the undershoot problem while maintaining smoothness. It is defined as a quartic C2-spline function constrained with first derivatives at tangential points that effectively avoids undershoot. The tangential points optimization method is proposed in combination with this spline to attain optimal smoothness of the estimated envelope.

Realizing directional sound source in FDTD method by estimating initial value

Takeuchi, Daiki; Yatabe, Kohei; Oikawa, Yasuhiro

ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings Peer Review Yes p.461 - 4652018/04-2018/04

DOIScopus

Detail

Publish Classification:Research paper (international conference proceedings)

Outline:Wave-based acoustic simulation methods are studied actively for predicting acoustical phenomena. Finite-difference time-domain (FDTD) method is one of the most popular methods owing to its straightforwardness of calculating an impulse response. In an FDTD simulation, an omnidirectional sound source is usually adopted, which is not realistic because the real sound sources often have specific directivities. However, there is very little research on imposing a directional sound source into FDTD methods. In this paper, a method of realizing a directional sound source in FDTD methods is proposed. It is formulated as an estimation problem of the initial value so that the estimated result corresponds to the desired directivity. The effectiveness of the proposed method is illustrated through some numerical experiments.

Modal decomposition of musical instrument sound via alternating direction method of multipliers

Masuyama, Yoshiki; Kusano, Tsubasa; Yatabe, Kohei; Oikawa, Yasuhiro

ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings Peer Review Yes p.631 - 6352018/04-2018/04

DOIScopus

Detail

Publish Classification:Research paper (international conference proceedings)

Outline:For a musical instrument sound containing partials, or modes, the behavior of modes around the attack time is particularly important. However, accurately decomposing it around the attack time is not an easy task, especially when the onset is sharp. This is because spectra of the modes are peaky while the sharp onsets need a broad one. In this paper, an optimization-based method of modal decomposition is proposed to achieve accurate decomposition around the attack time. The proposed method is formulated as a constrained optimization problem to enforce the perfect reconstruction property which is important for accurate decomposition. For optimization, the alternating direction method of multipliers (ADMM) is utilized, where the update of variables is calculated in closed form. The proposed method realizes accurate modal decomposition in the simulation and real piano sounds.

Parametric approximation of piano sound based on Kautz model with sparse linear prediction

Kobayashi, Kenji; Takeuchi, Daiki; Iwamoto, Mio; Yatabe, Kohei; Oikawa, Yasuhiro

ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings Peer Review Yes p.626 - 6302018/04-2018/04

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Publish Classification:Research paper (international conference proceedings)

Outline:The piano is one of the most popular and attractive musical instruments that leads to a lot of research on it. To synthesize the piano sound in a computer, many modeling methods have been proposed from full physical models to approximated models. The focus of this paper is on the latter, approximating piano sound by an IIR filter. For stably estimating parameters, the Kautz model is chosen as the filter structure. Then, the selection of poles and excitation signal rises as the questions which are typical to the Kautz model that must be solved. In this paper, sparsity based construction of the Kautz model is proposed for approximating piano sound.

Seeing the sound we hear: optical technologies for visualizing sound wave

Oikawa, Yasuhiro; Ishikawa, Kenji; Yatabe, Kohei; Onuma, Takashi; Niwa, Hayato

Proc. SPIE 10666, Three-Dimensional Imaging, Visualization, and Display 2018 Invitation Yes 10666p.10666-1 - 10666-82018/04-2018/04

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Publish Classification:Research paper (international conference proceedings)

Outline:Optical methods have been applied to visualize sound waves, and these have received a considerable amount of attention in both optical and acoustical communities. We have researched optical methods for sound imaging including laser Doppler vibrometry and Schlieren method. More recently, parallel phase-shifting interferometry with a high-speed polarization camera has been used, and it can take a slow-motion video of sound waves in the audible range. This presentation briefly reviews the recent progress in optical imaging of sound in air and introduces the applications including acoustic transducer testing and investigation of acoustic phenomena.

Simultaneous imaging of flow and sound using high-speed parallel phase-shifting interferometry

Ishikawa, Kenji; Tanigawa, Risako; Yatabe, Kohei; Oikawa, Yasuhiro; Onuma, Takashi; Niwa, Hayato

Optics Letters Peer Review Yes 43(5) p.991 - 9942018/03-2018/03

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Publish Classification:Research paper (scientific journal) ISSN:01469592

Outline:© 2018 Optical Society of America. In this Letter, simultaneous imaging of flow and sound by using parallel phase-shifting interferometry and a high-speed polarization camera is proposed. The proposed method enables the visualization of flow and sound simultaneously by using the following two factors: (i) injection of the gas, whose density is different from the surrounding air, makes the flow visible to interferometry, and (ii) time-directional processing is applied for extracting the small-amplitude sound wave from the high-speed flow video. An experiment with a frame rate of 42,000 frames per second for visualizing the flow and sound emitted from a whistle was conducted. By applying time-directional processing to the obtained video, both flow emitted from the slit of th e whistle and a spherical sound wave of 8.7 kHz were successively captured.

Infinite-dimensional SVD for revealing microphone array's characteristics

Koyano, Yuji; Yatabe, Kohei; Oikawa, Yasuhiro

Applied Acoustics Peer Review Yes 129p.116 - 1252018/01-2018/01

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Publish Classification:Research paper (scientific journal) ISSN:0003-682X

Outline:Nowadays, many acoustical applications utilize microphone arrays whose configurations have a lot of varieties including linear, planar, spherical and random arrays. Arguably, some configurations are better than the others in terms of acquiring the spatial information of a sound field (for example, a spherical array can distinguish any direction of arrival, while a linear array cannot distinguish the direction perpendicular to its aperture direction due to the rotational symmetry). However, it is not easy to compare arrays of different configurations because each array has been treated by a specific theory depending on the configuration of the array. Although several criteria have been proposed for evaluating and/or designing the arrays, most of them are application-oriented criteria, and the best configuration for some criterion may not be a better one for the other criterion. Therefore, an analysis method for microphone arrays which does not depend on the array configuration or application is necessary. In this paper, the infinite-dimensional SVD is proposed for analyzing and comparing the properties of arrays. The singular values, functions and vectors obtained by the proposed method provide the fundamental properties of an array.

Simultaneous visualization of flow and sound using parallel phase-shifting interferometry

Tanigawa, Risako; Ishikawa, Kenji; Yatabe, Kohei; Oikawa, Yasuhiro; Onuma, Takashi; Niwa, Hayato

11th Pacific Symposium on Flow Visualization and Image Processing (PSFVIP) p.031-1 - 031-42017/12-2017/12

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Publish Classification:Research paper (international conference proceedings)

Outline:Aerodynamic sound generated by flow is one of the causes of noise; thus its prediction and reduction are essential. Optical visualization techniques are effective to understand the sound generation process caused by flow. In order to understand the generation process of aerodynamic sound, simultaneous visualization of flow and sound is necessary. However, simultaneous optical visualization of flow and sound has not been accomplished because the transient sound field measurement has just recently been realized. This paper aims to simultaneously visualize both flow and sound. In order to realize this purpose, parallel phase-shifting interferometry (PPSI) which can measure transient field is suitable. As a basic experiment of simultaneous visualization using PPSI, the flow and sound field around a whistle were visualized.

Hyper ellipse fitting in subspace method for phase-shifting interferometry: Practical implementation with automatic pixel selection

Yatabe, Kohei; Ishikawa, Kenji; Oikawa, Yasuhiro

Optics Express Peer Review Yes 25(23) p.29401 - 294162017/11-2017/11

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Publish Classification:Research paper (scientific journal)

Outline:© 2017 Optical Society of America. This paper presents a method of significantly improving the previously proposed simple, flexible, and accurate phase retrieval algorithm for the random phase-shifting interferometry named HEFS [K. Yatabe, J. Opt. Soc. Am. A 34, 87 (2017)]. Although its e ectiveness and performance were confirmed by numerical experiments in the original paper, it is found that the algorithm may not work properly if observed fringe images contains untrusted (extremely noisy) pixels. In this paper, a method of avoiding such untrusted pixels within the estimation processes of HEFS is proposed for the practical use of the algorithm. In addition to the proposal, an experiment of measuring a sound field in air was conducted to show the performance for real data, where the proposed improvement is critical for that situation. MATLAB codes (which can be downloaded from http://goo.gl/upcsFe) are provided within the paper to aid understanding the main concept of the proposed methods.

Experimental visualization of flow-induced sound using high-speed polarization interferometer

Ishikawa, Kenji; Tanigawa, Risako; Yatabe, Kohei; Oikawa, Yasuhiro; Onuma, Takashi; Niwa, Hayato

14th International Conference on Flow Dynamics (ICFD) p.746 - 7472017/11-2017/11

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Publish Classification:Research paper (international conference proceedings)

Outline:An experimental method to visualize a sound field generated by flow is presented. The high-speed polarization interferometer is used to detect the change in refractive index caused by the sound wave. This paper demonstrates the visualization of acoustic resonance induced by air flow inside a rectangular cavity with a circular orifice. Two acoustic resonance modes, namely Helmholtz resonance and duct resonance, were successfully captured by the experiment. The proposed method should be effectively used to understand the physics of the interaction between flow and sound.

Visualization of 3D sound field using see-through head mounted display

Inoue, Atsuto; Yatabe, Kohei; Oikawa, Yasuhiro; Ikeda, Yusuke

Proceedings of SIGGRAPH ’17 Posters Peer Review Yes p.34-1 - 34-22017/07-2017/07

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Publish Classification:Research paper (international conference proceedings)

Outline:© 2017 Copyright held by the owner/author(s). We propose a visualization system of three-dimensional (3D) sound information using video and optical see-through head mounted displays (ST-HMDs). The Mixed Reality (MR) displays enable intuitive understanding of 3D information of a sound field which is quite difficult to project onto an ordinary two-dimensional (2D) display in an easily understandable way. As examples of the visualization, the sound intensity (a stationary vector field representing the energy flow of sound) around a speaker and a motor engine is shown.

Least-squares estimation of sound source directivity using convex selector of a better solution

Tamura, Yuki; Yatabe, Kohei; Oikawa, Yasuhiro

Acoustical Science and Technology Peer Review Yes 38(3) p.128 - 1362017/05-2017/05

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Publish Classification:Research paper (scientific journal) ISSN:13463969

Outline:Many acoustical simulation methods have been studied to investigate acoustical phenomena. Modeling of the directivity pattern of a sound source is also important for obtaining realistic simulation results. However, there has been little research on this. Although there has been research on sound source identification, the results might not be in a suitable form for numerical simulation. In this paper, a method for modeling a sound source from measured data is proposed. It utilizes the sum of monopoles as the physical model, and the modeling is achieved by estimating the model parameters. The estimation method is formulated as a convex optimization problem by assuming the smoothness of a solution and the sparseness of parameters. Moreover, an algorithm based on the alternating direction method of multipliers (ADMM) for solving the problem is derived. The validity of the method is evaluated using simulated data, and the modeling result for an actual loudspeaker is shown.

Acousto-optic back-projection: Physical-model-based sound field reconstruction from optical projections

Yatabe, Kohei; Ishikawa, Kenji; Oikawa, Yasuhiro

Journal of Sound and Vibration Peer Review Yes 394p.171 - 1842017/04-2017/04

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Publish Classification:Research paper (scientific journal) ISSN:0022460X

Outline:© 2017 Elsevier LtdAs an alternative to microphones, optical techniques have been studied for measuring a sound field. They enable contactless and non-invasive acoustical observation by detecting density variation of medium caused by sound. Although they have important advantages comparing to microphones, they also have some disadvantages. Since sound affects light at every points on the optical path, the optical methods observe an acoustical quantity as spatial integration. Therefore, point-wise information of a sound field cannot be obtained directly. Ordinarily, the computed tomography (CT) method has been applied for reconstructing a sound field from optically measured data. However, the observation process of the optical methods have not been considered explicitly, which limits the accuracy of the reconstruction. In this paper, a physical-model-based sound field reconstruction method is proposed. It explicitly formulates the physical observation process so that a model mismatch of the conventional methods is eliminated.

Infinite-dimensional SVD for analyzing microphone array

Koyano, Yuji; Yatabe, Kohei; Oikawa, Yasuhiro

ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings Peer Review Yes p.176 - 1802017/03-2017/03

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Publish Classification:Research paper (international conference proceedings) ISSN:15206149

Outline:Nowadays, various types of microphone array are used in many applications. However, it is not easy to compare arrays of different types because each array has been treated by a specific theory depending on the type of an array. Although several criteria have been proposed for microphone arrays for evaluating and/or designing an array, most of them are application-oriented criteria and the best configuration for some criterion may not be a better one in the other criterion. Therefore, an analysis and comparing method for microphone arrays which does not depend on an array configuration and application are necessary. In this paper, infinite-dimensional SVD is proposed for analyzing and comparing properties of arrays. The singular values and functions obtained by proposed method show sampling property of an array and can be unified criterion.

Coherence-adjusted monopole dictionary and convex clustering for 3D localization of mixed near-field and far-field sources

Tachikawa, Tomoya; Yatabe, Kohei; Oikawa, Yasuhiro

ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings Peer Review Yes p.3191 - 31952017/03-2017/03

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Publish Classification:Research paper (international conference proceedings) ISSN:15206149

Outline:In this paper, 3D sound source localization method for simultaneously estimating both direction-of-arrival (DOA) and distance from the microphone array is proposed. For estimating distance, the off-grid problem must be overcome because the range of distance to be considered is quite broad and even not bounded. The proposed method estimates positions based on an extension of the convex clustering method combined with sparse coefficients estimation. A method for constructing a suitable monopole dictionary based on coherence is also proposed so that the convex clustering based method appropriately estimate distance of sound sources. Numerical experiments of distance estimation and 3D localization show possibility of the proposed method.

Spatio-temporal filter bank for visualizing audible sound field by Schlieren method

Chitanont, Nachanant; Yatabe, Kohei; Ishikawa, Kenji; Oikawa, Yasuhiro

Applied Acoustics Peer Review Yes 115p.109 - 1202017/01-2017/01

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Publish Classification:Research paper (scientific journal) ISSN:0003682X

Outline:© 2016 Elsevier LtdVisualization of sound field using optical techniques is a powerful tool for understanding acoustical behaviors. It uses light waves to examine the acoustical quantities without disturbing the sound information of the field under investigation. Schlieren imaging is an optical method that uses a camera to visualize the density of transparent media. As it uses a single shot to capture the information without scanning, it can observe both reproducible and non-reproducible sound field. Conventionally, the Schlieren system is applied to high-pressure ultrasound and shock waves. However, since the density variation of air caused by the audible sound field is very small, this method was not applicable for visualizing these fields. In this paper, a spatio-temporal filter bank is proposed to overcome this problem. As the sound is a very specific signal, the spatio-temporal spectrum (in two-dimensional space and time) of the audible sound is concentrated in a specific region. The spatio-temporal filter bank is designed for extracting the sound field information in the specific region and removing noise. The results indicate that the visibility of the sound fields is enhanced by using the proposed method.

Simple, flexible, and accurate phase retrieval method for generalized phase-shifting interferometry

Yatabe, Kohei; Ishikawa, Kenji; Oikawa, Yasuhiro

Journal of the Optical Society of America A: Optics and Image Science, and Vision Peer Review Yes 34(1) p.87 - 962017/01-2017/01

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Publish Classification:Research paper (scientific journal) ISSN:10847529

Outline:© 2016 Optical Society of America.This paper presents a non-iterative phase retrieval method from randomly phase-shifted fringe images. By combining the hyperaccurate least squares ellipse fitting method with the subspace method (usually called the principal component analysis), a fast and accurate phase retrieval algorithm is realized. The proposed method is simple, flexible, and accurate. It can be easily coded without iteration, initial guess, or tuning parameter. Its flexibility comes from the fact that totally random phase-shifting steps and any number of fringe images greater than two are acceptable without any specific treatment. Finally, it is accurate because the hyperaccurate least squares method and the modified subspace method enable phase retrieval with a small error as shown by the simulations. A MATLAB code, which is used in the experimental section, is provided within the paper to demonstrate its simplicity and easiness.

Interferometric imaging of acoustical phenomena using high-speed polarization camera and 4-step parallel phase-shifting technique

Ishikawa, Kenji; Yatabe, Kohei; Ikeda, Yusuke; Oikawa, Yasuhiro; Onuma, Takashi; Niwa, Hayato; Yoshii, Minoru

Proceedings of SPIE - The International Society for Optical Engineering Peer Review Yes 103282017/01-2017/01

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Publish Classification:Research paper (international conference proceedings) ISSN:0277786X

Outline:© 2017 SPIE.Imaging of sound aids the understanding of the acoustical phenomena such as propagation, reflection, and diffraction, which is strongly required for various acoustical applications. The imaging of sound is commonly done by using a microphone array, whereas optical methods have recently been interested due to its contactless nature. The optical measurement of sound utilizes the phase modulation of light caused by sound. Since light propagated through a sound field changes its phase as proportional to the sound pressure, optical phase measurement technique can be used for the sound measurement. Several methods including laser Doppler vibrometry and Schlieren method have been proposed for that purpose. However, the sensitivities of the methods become lower as a frequency of sound decreases. In contrast, since the sensitivities of the phase-shifting technique do not depend on the frequencies of sounds, that technique is suitable for the imaging of sounds in the low-frequency range. The principle of imaging of sound using parallel phase-shifting interferometry was reported by the authors (K. Ishikawa et al., Optics Express, 2016). The measurement system consists of a high-speed polarization camera made by Photron Ltd., and a polarization interferometer. This paper reviews the principle briefly and demonstrates the high-speed imaging of acoustical phenomena. The results suggest that the proposed system can be applied to various industrial problems in acoustical engineering.

Signal processing for optical sound field measurement and visualization

Yatabe, Kohei; Ishikawa, Kenji; Oikawa, Yasuhiro

Proceedings of Meetings on Acoustics Invitation Yes 29(1) p.020010-1 - 020010-82016/11-2016/11

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Publish Classification:Research paper (international conference proceedings) ISSN:1939800X

Outline:© 2017 Acoustical Society of America. Accurately measuring sound pressure is not an easy task because every microphone has its own mechanical and electrical characteristics. Moreover, the existence of a measuring instrument inside the field causes reflection and diffraction which deform the wavefront of sound to be measured. Ideally, a sensing device should not have any characteristic nor exist inside a measuring region. Although it may sound unrealistic, optical measurement methods are able to realize such ideal situation. Optical devices can be placed outside the sound field, and some of the sensing techniques, which decode information of sound from the phase of light, are able to cancel optical and electrical characteristics. Thus, optical sound measurement methods have possibility of achieving higher accuracy than ordinary sound measurement in principle. However, they have two main drawbacks that have prevented their applications in acoustics: (1) point-wise information cannot be obtained directly because observed signal is spatially integrated along the optical path; and (2) increasing signal-to-noise ratio is difficult because optical measurement of less than a nanometer order is typically required. To overcome the above difficulties, we have proposed several signal processing methods. In this paper, those methods are introduced with the physical principle of optical sound measurement.

Three-dimensional sound-field visualization system using head mounted display and stereo camera

Inoue, Atsuto; Ikeda, Yusuke; Yatabe, Kohei; Oikawa, Yasuhiro

Proceedings of Meetings on Acoustics 29(1) p.025001-1 - 025001-132016/11-2016/11

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Publish Classification:Research paper (international conference proceedings) ISSN:1939800X

Outline:© 2017 Acoustical Society of America. Visualization of a sound field helps us to intuitively understand various acoustic phenomena in sound design and education. The most straightforward method is to overlap the measured data onto a photographic image. However, in order to understand an entire three-dimensional (3D) sound field by using a conventional two-dimensional screen, it is necessary to move a camera and measure repeatedly. On the other hand, the augmented reality (AR) techniques such as an video see-through head mounted display (VST-HMD) have been rapidly developed. In this study, we propose a sound field visualization system using an VST-HMD and a hand held four-point microphone. This system calculates sound intensity from the four sound signals in real time. Then, the sound intensity distribution is depicted as arrows in the 3D display. The position and angle of the microphones and users head are acquired via AR markers and head tracking sensors of the VST-HMD. The system realizes simple and effective visualization of 3D sound field information from the various directions and positions of view. For the experiments, the sound fields generated by loudspeakers and motorcycles were visualized. The results suggested that the proposed system can present information of the field in easily recognizable manner.

Optical sensing of sound fields: non-contact, quantitative, and single-shot imaging of sound using high-speed polarization camera

Ishikawa, Kenji; Yatabe, Kohei; Ikeda, Yusuke; Oikawa, Yasuhiro; Onuma, Takashi; Niwa, Hayato; Yoshii, Minoru

Proceedings of Meetings on Acoustics Invitation Yes 29(1) p.030005-1 - 030005-82016/11-2016/11

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Publish Classification:Research paper (international conference proceedings) ISSN:1939800X

Outline:© 2017 Acoustical Society of America. Imaging of a sound field aids understanding of the actual behavior of the field. That is useful for obtaining acoustical spatial characteristics of transducers, materials and noise sources. For high spatial resolution imaging, optical measurement methods have been used thanks to its contactless nature. This paper presents sound field imaging method based on parallel phase-shifting interferometry, which enables to acquire an instantaneous two-dimensional phase distribution of light. Information of sound field is calculated from the phase of light based on the acousto-optic theory. The system consists of a polarization interferometer and high-speed polarization camera. The number of the measurement points in a single image are 512 × 512 and the interval between adjacent pixels is 0.22 mm. Therefore, the system can image a sound field with much higher spatial resolution compared with conventional imaging methods such as microphone arrays. The maximum frame rate, which is corresponding to the sampling frequency, is 1.55 M frames per second. This paper contains the principle of optical measurement of sound, the description of the system, and several experimental results including imaging of sound fields generated by transducers and reflection of the sound waves.

Sound source localization based on sparse estimation and convex clustering

Tachikawa, Tomoya; Yatabe, Kohei; Ikeda, Yusuke; Oikawa, Yasuhiro

Proceedings of Meetings on Acoustics 29(1) p.055004-1 - 055004-142016/11-2016/11

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Publish Classification:Research paper (international conference proceedings) ISSN:1939800X

Outline:Sound source localization techniques using microphones have been the subject of much interest for many years. Many of them assume far-field sources, and plane waves are used as a dictionary for estimating the direction-of-arrival (DOA) of sound sources. On the other hand, there has been less research on 3D source localization which estimates both direction and distance. In case of estimating distances, monopoles must be used as a dictionary. By setting monopoles in far-field, their waves can be regarded as plane waves, and their distance can be estimated.However, monopoles set at many positions can be impossible due to high computational cost. Moreover, the grid discretization can cause estimation error because there are a lot of the number of grid points in 3D space. Such discretization issue is called off-grid problem. Therefore, a source localization with monopole-only dictionary needs some methods to solve the off-grid problem.The proposed method uses sparse estimation and modified convex clustering with a monopole-only dictionary. Sparse estimation selects the monopoles which are candidates of the source positions. Then, modified convex clustering solves the off-grid problem, and estimates source positions. In this paper, simulation and comparison with another method show effectiveness of the proposed method.

Improving principal component analysis based phase extraction method for phase-shifting interferometry by integrating spatial information

Yatabe, Kohei; Ishikawa, Kenji; Oikawa, Yasuhiro

Optics Express Peer Review Yes 24(20) p.22881 - 228912016/10-2016/10

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Publish Classification:Research paper (scientific journal)

Outline:© 2016 Optical Society of America.Phase extraction methods based on the principal component analysis (PCA) can extract objective phase from phase-shifted fringes without any prior knowledge about their shift steps. Although it is fast and easy to implement, many fringe images are needed for extracting the phase accurately from noisy fringes. In this paper, a simple extension of the PCA method for reducing extraction error is proposed. It can effectively reduce influence from random noise, while most of the advantages of the PCA method is inherited because it only modifies the construction process of the data matrix from fringes. Although it takes more time because size of the data matrix to be decomposed is larger, computational time of the proposed method is shown to be reasonably fast by using the iterative singular value decomposition algorithm. Numerical experiments confirmed that the proposed method can reduce extraction error even when the number of interferograms is small.

Compensation of fringe distortion for phaseshifting three-dimensional shape measurement by inverse map estimation

Yatabe, Kohei; Ishikawa, Kenji; Oikawa, Yasuhiro

Applied Optics Peer Review Yes 55(22) p.6017 - 60242016/08-2016/08

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Publish Classification:Research paper (scientific journal) ISSN:1559128X

Outline:© 2016 Optical Society of America.For three-dimensional shape measurement, phase-shifting techniques are widely used to recover the objective phase containing height information from images of projected fringes. Although such techniques can provide an accurate result in theory, there might be considerable error in practice. One main cause of such an error is distortion of fringes due to nonlinear responses of a measurement system. In this paper, a postprocessing method for compensating distortion is proposed. Compared to other compensation methods, the proposed method is flexible in two senses: (1) no specific model of nonlinearity (such as the gamma model) is needed, and (2) no special calibration data are needed (only the observed image of the fringe is required). Experiments using simulated and real data confirmed that the proposed method can compensate multiple types of nonlinearity without being concerned about the model.

Optical sound field measurement and imaging using laser and high-speed camera

Oikawa, Yasuhiro; Yatabe, Kohei; Ishikawa, Kenji; Ikeda, Yusuke

Proceedings of the INTER-NOISE 2016 - 45th International Congress and Exposition on Noise Control Engineering: Towards a Quieter Future Invitation Yes p.258 - 2662016/08-2016/08

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Detail

Publish Classification:Research paper (international conference proceedings)

Outline:© 2016, German Acoustical Society (DEGA). All rights reserved.Optical sound measurement, which acquires acoustical quantities by means of optical techniques, is of growing interest as an alternative method for the sound field imaging. There are two remarkable aspects of the optical sound measurement. The first is non-intrusiveness. Since the measurement is achieved by observing the light passed through the sound field, the instruments can be arranged outside the measurement field; non-contact and non-destructive measurement can be achieved. The second one is spatial resolution. Instead of building an array, expanding or scanning of light are often used for the optical imaging. Therefore, the optical imaging does not have the limitation of interval of measurement points due to the size of the instruments as microphone arrays. These two aspects make the optical method possible to image sound field with high spatial resolution and without any disturbance to the original field. In this paper, we show several methods for the optical sound imaging. Laser Doppler vibrometer can be developed as the imaging methods by scanning a narrow light beam. The two dimensional of transient field measurement can be achieved by using a high-speed camera because of single-shot. In addition some signal processing techniques introduced to optical measurement are also described.

Convex optimization-based windowed Fourier filtering with multiple windows for wrapped-phase denoising

Yatabe, Kohei; Oikawa, Yasuhiro

Applied Optics Peer Review Yes 55(17) p.4632 - 46412016/06-2016/06

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Publish Classification:Research paper (scientific journal) ISSN:1559128X

Outline:© 2016 Optical Society of America.The windowed Fourier filtering (WFF), defined as a thresholding operation in the windowed Fourier transform (WFT) domain, is a successful method for denoising a phase map and analyzing a fringe pattern. However, it has some shortcomings, such as extremely high redundancy, which results in high computational cost, and difficulty in selecting an appropriate window size. In this paper, an extension of WFF for denoising a wrapped-phase map is proposed. It is formulated as a convex optimization problem using Gabor frames instead of WFT. Two Gabor frames with differently sized windows are used simultaneously so that the above-mentioned issues are resolved. In addition, a differential operator is combined with a Gabor frame in order to preserve discontinuity of the underlying phase map better. Some numerical experiments demonstrate that the proposed method is able to reconstruct a wrapped-phase map, even for a severely contaminated situation.

High-speed imaging of sound using parallel phase-shifting interferometry

Ishikawa, Kenji; Yatabe, Kohei; Chitanont, Nachanant; Ikeda, Yusuke; Oikawa, Yasuhiro; Onuma, Takashi; Niwa, Hayato; Yoshii, Minoru

Optics Express Peer Review Yes 24(12) p.12922 - 129322016/06-2016/06

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Publish Classification:Research paper (scientific journal)

Outline:© 2016 Optical Society of America.Sound-field imaging, the visualization of spatial and temporal distribution of acoustical properties such as sound pressure, is useful for understanding acoustical phenomena. This study investigated the use of parallel phase-shifting interferometry (PPSI) with a high-speed polarization camera for imaging a sound field, particularly high-speed imaging of propagating sound waves. The experimental results showed that the instantaneous sound field, which was generated by ultrasonic transducers driven by a pure tone of 40 kHz, was quantitatively imaged. Hence, PPSI can be used in acoustical applications requiring spatial information of sound pressure.

Physical-model based efficient data representation for many-channel microphone array

Koyano, Yuji; Yatabe, Kohei; Ikeda, Yusuke; Oikawa, Yasuhiro

ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings Peer Review Yes 2016-Mayp.370 - 3742016/05-2016/05

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Publish Classification:Research paper (international conference proceedings) ISSN:15206149

Outline:© 2016 IEEE.Recent development of microphone arrays which consist of more than several tens or hundreds microphones enables acquisition of rich spatial information of sound. Although such information possibly improve performance of any array signal processing technique, the amount of data will increase as the number of microphones increases; for instance, a 1024 ch MEMS microphone array, as in Fig. 1, generates data more than 10 GB per minute. In this paper, a method constructing an orthogonal basis for efficient representation of sound data obtained by the microphone array is proposed. The proposed method can obtain a basis for arrays with any configuration including rectangle, spherical, and random microphone array. It can also be utilized for designing a microphone array because it offers a quantitative measure for comparing several array configurations.

Eigenanalysis of lp-norm ball-shaped room using the method of particular solutions

Yatabe, Kohei; Oikawa, Yasuhiro

12th Western Pacific Acoustics Conference (WESPAC 2015) p.88 - 922015/12-2015/12

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Publish Classification:Research paper (international conference proceedings)

Numerical analysis of acousto-optic effect caused by audible sound based on geometrical optics

Ishikawa, Kenji; Yatabe, Kohei; Ikeda, Yusuke; Oikawa, Yasuhiro

12th Western Pacific Acoustics Conference (WESPAC 2015) p.165 - 1692015/12-2015/12

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Publish Classification:Research paper (international conference proceedings)

Audible sound field visualization by using Schlieren technique

Chitanont, Nachanant; Yatabe, Kohei; Oikawa, Yasuhiro

12th Western Pacific Acoustics Conference (WESPAC 2015) p.5 - 92015/12-2015/12

DOI

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Publish Classification:Research paper (international conference proceedings)

Extracting sound information from high-speed video using 3-D shape measurement method

Yamanaka, Yusei; Yatabe, Kohei; Nakamura, Ayumi; Ikeda, Yusuke; Oikawa, Yasuhiro

12th Western Pacific Acoustics Conference (WESPAC 2015) p.30 - 342015/12-2015/12

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Publish Classification:Research paper (international conference proceedings)

Calculation of impulse response by using the method of fundamental solutions

Suzuki, Naoko; Yatabe, Kohei; Oikawa, Yasuhiro

12th Western Pacific Acoustics Conference (WESPAC 2015) p.388 - 3922015/12-2015/12

DOI

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Publish Classification:Research paper (international conference proceedings)

Modeling of free-reed instrument considering mechanical nonlinearity of the reed

Nakamura, Ayumi; Yamanaka, Yusei; Yatabe, Kohei; Oikawa, Yasuhiro

12th Western Pacific Acoustics Conference (WESPAC 2015) p.206 - 2092015/12-2015/12

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Publish Classification:Research paper (international conference proceedings)

Optically visualized sound field reconstruction using Kirchhoff-Helmholtz equation

Yatabe, Kohei; Oikawa, Yasuhiro

Acoustical Science and Technology Peer Review Yes 36(4) p.351 - 3542015/01-2015/01

DOIScopus

Detail

Publish Classification:Research paper (scientific journal) ISSN:13463969

Outline:A method for reconstructing a measured sound field using the Kirchhoff-Helmholtz boundary integral equation is presented. L4-norm ball shape was chosen for the boundary, which is smooth and more suitable for data measured along the rectangular coordinate than the circle. ADMM (alternating direction method of multipliers) was employed to solve the initial value estimation via sparsity and the norm ball constrained least squares problem. The experiment using synthetic data confirmed the effectiveness of the method.

Redundant representation of acoustic signals using curvelet transform and its application to speech denoising

Chiba, Mariko; Yatabe, Kohei; Oikawa, Yasuhiro

Acoustical Science and Technology Peer Review Yes 36(5) p.457 - 4582015/01-2015/01

DOIScopus

Detail

Publish Classification:Research paper (scientific journal) ISSN:13463969

Outline:A study is conducted to propose a sparse representation method for acoustic signals by the use of curvelets, and confirm its efficacy through an example of speech denoising. The curvelet denoising method was applied using the hard thresholding to speech, to demonstrate the effectiveness of the proposed representation. The method was applied to a female speech with additive pink noise for conducting the investigations. The level of the noise was chosen so that signal-to-noise ratio (SNR) became 10 dB. The thresholding process was iterated 10 times. The same input signal was processed by two denoising Methods for comparison.

Optically visualized sound field reconstruction based on sparse selection of point sound sources

Yatabe, Kohei; Oikawa, Yasuhiro

ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings Peer Review Yes 2015-Augustp.504 - 5082015/01-2015/01

DOIScopus

Detail

Publish Classification:Research paper (international conference proceedings) ISSN:15206149

Outline:© 2015 IEEE.Visualization is an effective way to understand the behavior of a sound field. There are several methods for such observation including optical measurement technique which enables a non-destructive acoustical observation by detecting density variation of the medium. For audible sound propagating through the air, however, smallness of the variation requires high sensitivity of the measuring system that causes problematic noise contamination. In this paper, a method for reconstructing two-dimensional audible sound fields from noisy optical observation is proposed.

Visualization of sound field by means of Schlieren method with spatio-temporal filtering

Chitanont, Nachanant; Yaginuma, Keita; Yatabe, Kohei; Oikawa, Yasuhiro

ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings Peer Review Yes 2015-Augustp.509 - 5132015/01-2015/01

DOIScopus

Detail

Publish Classification:Research paper (international conference proceedings) ISSN:15206149

Outline:© 2015 IEEE.Visualization of sound field using Schlieren technique provides many advantages. It enables us to investigate the change of the sound field in real-time from every point of the observing region. However, since the density gradient of air caused by the disturbance of acoustic field is very small, it is difficult to observe the audible sound field from the raw Schlieren video. In this paper, to enhance visibility of the audible sound fields from the Schlieren videos, we propose to use spatio-temporal filters for extracting sound information and for noise removal. We have utilized different filtering techniques such as the FIR bandpass filter, the Gaussian filter, the Wiener filter and the 3D Gabor filter, to do this. The results indicate that the data observed after using these signal processing methods are clearer than the raw Schlieren videos.

PDE-based interpolation method for optically visualized sound field

Yatabe, Kohei; Oikawa, Yasuhiro

ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings Peer Review Yes p.4738 - 47422014/01-2014/01

DOIScopus

Detail

Publish Classification:Research paper (international conference proceedings) ISSN:15206149

Outline:An effective way to understand the behavior of a sound field is to visualize it. An optical measurement method is a suitable option for this as it enables contactless non-destructive measurement. After measuring a sound field, interpolation of the data is necessary for a smooth visualization. However, conventional interpolation methods cannot provide a physically meaningful result especially when the condition of the measurement causes moiré effect. In this paper, a special interpolation method for an optically visualized sound field based on the Kirchhoff-Helmholtz integral equation is proposed. © 2014 IEEE.

Acoustic Yagi-Uda antenna using resonance tubes

Tamura, Yuki; Yatabe, Kohei; Ouchi, Yasuhiro; Oikawa, Yasuhiro; Yamasaki, Yoshio

INTERNOISE 2014 - 43rd International Congress on Noise Control Engineering: Improving the World Through Noise Control 2014/01-2014/01

Scopus

Detail

Publish Classification:Research paper (international conference proceedings)

Outline:A Yagi-Uda antenna gets high directivity by applying current phase shift between elements due to resonance phenomena. It has some directors and reflectors, which are elements without electric supply. The length of directors is shorter than half-wave and that of reflectors is longer than half-wave. We proposed an acoustic Yagi-Uda antenna which elements are resonance tubes and a loudspeaker. The aim of this research is to im- prove directivity in a specific frequency. This can be applied to Radio Acoustic Sounding System (RASS), which is a kind of radar for weather observation, or to a parametric loudspeaker. The phase shift of sound waves was observed in the condition with a resonance tube and without the tube at the same position. That shift changes suddenly around the resonance frequency of the tube. Our acoustic antenna has resonance tubes that have different length as directors and reflectors to apply this phenomenon. Moreover, the distances be- Tween a loudspeaker and tubes were concerned by some experiments and by numerical analysis. The acoustic antenna showed directivity in an appropriate condition of the distances and the frequency of the sound source. It will be also added the consideration about the effective frequency band of this acoustic antenna.

Wind noise reduction using empirical mode decomposition

Yatabe, Kohei; Oikawa, Yasuhiro

Proceedings of Meetings on Acoustics 192013/06-2013/06

DOIScopus

Detail

Publish Classification:Research paper (international conference proceedings) ISSN:1939800X

Outline:One common problem of outdoor recordings is a contamination of wind noise which has highly non-stationary characteristics. Although there are a lot of noise reduction methods which work well for general kinds of noises, most methods perform worse for wind noise due to its non-stationary nature. Therefore, wind noise reduction need specific technique to overcome this non-stationary. Empirical mode decomposition (EMD) is a relatively new method to decompose a signal into several data-driven bases which are modeled as amplitude and frequency modulated sinusoids that represent wind noise better than quasi-stationary analysis methods such as short-time Fourier transform since it assumes an analyzing signal as non-stationary. Thus, EMD has a potential to reduce wind noise from recorded sounds in an entirely different way from ordinary methods. In this paper, the method to apply EMD as a wind noise suppressor is presented. The experiment is performed on a female speech superimposed with wind noise, and the results showed its possibility. © 2013 Acoustical Society of America.

Books And Publication

Acousticpedia for Begineers

Acoustical Society of Japan(Sharing writing)

CORONA PUBLISHING CO.,LTD.2017/03-2017/03

Detali

Total Number of Pages:206ISBN:978-4-339-00895-1

Acoustic Keyword Book

Acoustical Society Japan(Sharing writing)

CORONA PUBLISHING CO.,LTD.2016/03-2016/03

Detali

Total Number of Pages:494ISBN:978-4-339-00880-7

On-campus Research System

Special Research Project

凸最適化に基づく音響信号処理の研究

2017

Research Results Outline: 信号処理では,解くべき問題を最適化問題に帰着させ,何らかのアルゴリズムによって最適化することで,データに対して所望の処理を行うことが多い.最適化問題 信号処理では,解くべき問題を最適化問題に帰着させ,何らかのアルゴリズムによって最適化することで,データに対して所望の処理を行うことが多い.最適化問題は,非凸な問題と凸な問題に大別でき,凸なら大域最適性を保証できるなど,凸最適化問題は非凸な問題に比... 信号処理では,解くべき問題を最適化問題に帰着させ,何らかのアルゴリズムによって最適化することで,データに対して所望の処理を行うことが多い.最適化問題は,非凸な問題と凸な問題に大別でき,凸なら大域最適性を保証できるなど,凸最適化問題は非凸な問題に比べて性質の良い問題と言える.本研究では,音響信号処理の諸問題を凸最適化問題として定式化し,凸最適化アルゴリズムを用いて解くことで,様々な処理を実現した.具体的には,混合音から混合元の音源を推定する音源分離,観測信号から雑音を取り除くノイズ除去,音を調波成分に分けるモード分解,音響シミュレーションにおける初期条件の推定,実信号の包絡推定等を提案した.

近接分離最適化による音響信号処理

2018

Research Results Outline: 信号処理では,解決すべき課題を最適化問題に帰着させ,何らかのアルゴリズムによって解くことで,データに対して所望の処理を行うことが多い.最適化問題は, 信号処理では,解決すべき課題を最適化問題に帰着させ,何らかのアルゴリズムによって解くことで,データに対して所望の処理を行うことが多い.最適化問題は,複数の項が含まれると解くのが難しくなるが,近年の近接分離最適化手法は各項を分離して各々解くのみで良... 信号処理では,解決すべき課題を最適化問題に帰着させ,何らかのアルゴリズムによって解くことで,データに対して所望の処理を行うことが多い.最適化問題は,複数の項が含まれると解くのが難しくなるが,近年の近接分離最適化手法は各項を分離して各々解くのみで良く,複雑な問題を解くのに適している.本研究では,音響における諸問題を近接分離アルゴリズムを用いて解くことで,様々な音響信号処理を実現した.具体的には,混合音から混合元の音源を推定する音源分離,観測信号から雑音を取り除くノイズ除去,音の鳴っている位置を推定する音源定位,振幅スペクトログラムから位相を生成する位相復元などを提案した.

Lecture Course

Course TitleSchoolYearTerm
Introduction to media processing technologiesSchool of Fundamental Science and Engineering2019spring semester
Introduction to media processing technologiesSchool of Creative Science and Engineering2019spring semester
Introduction to media processing technologiesSchool of Advanced Science and Engineering2019spring semester
Science and Engineering Laboratory 1ASchool of Fundamental Science and Engineering2019spring semester
Science and Engineering Laboratory 1A VSchool of Fundamental Science and Engineering2019spring semester
Science and Engineering Laboratory 1ASchool of Creative Science and Engineering2019spring semester
Science and Engineering Laboratory 1A VSchool of Creative Science and Engineering2019spring semester
Science and Engineering Laboratory 1ASchool of Advanced Science and Engineering2019spring semester
Science and Engineering Laboratory 1A VSchool of Advanced Science and Engineering2019spring semester
Science and Engineering LaboratorySchool of Fundamental Science and Engineering2019fall semester
Science and Engineering Laboratory 1BSchool of Fundamental Science and Engineering2019fall semester
Science and Engineering Laboratory 1B VSchool of Fundamental Science and Engineering2019fall semester
Science and Engineering LaboratorySchool of Creative Science and Engineering2019fall semester
Science and Engineering Laboratory 1BSchool of Creative Science and Engineering2019fall semester
Science and Engineering Laboratory 1B VSchool of Creative Science and Engineering2019fall semester
Science and Engineering LaboratorySchool of Advanced Science and Engineering2019fall semester
Science and Engineering Laboratory 1BSchool of Advanced Science and Engineering2019fall semester
Science and Engineering Laboratory 1B VSchool of Advanced Science and Engineering2019fall semester
Basic mathematics for intermedia studiesSchool of Fundamental Science and Engineering2019spring semester
Engineering AcousticsSchool of Fundamental Science and Engineering2019fall semester
Acoustic SystemsSchool of Fundamental Science and Engineering2019fall semester
Laboratory for Advanced Science and Engineering ASchool of Advanced Science and Engineering2019spring quarter
Laboratory for Advanced Science and Engineering ASchool of Advanced Science and Engineering2019spring quarter
Laboratory for Advanced Science and Engineering ASchool of Advanced Science and Engineering2019spring quarter
Laboratory for Advanced Science and Engineering BSchool of Advanced Science and Engineering2019summer quarter
Laboratory for Advanced Science and Engineering BSchool of Advanced Science and Engineering2019summer quarter
Laboratory for Advanced Science and Engineering BSchool of Advanced Science and Engineering2019summer quarter