中川 誠司

Bone-conducted ultrasound (BCU) is perceived even by the profoundly sensorineural deaf. A novel hearing aid using the perception of amplitude-modulated BCU (BCU hearing aid: BCUHA) has been developed; however, further improvements are needed, especially in terms of articulation and sound quality. In this study, the intelligibility and sound quality of BCU speech with several types of amplitude modulation [double-sideband with transmitted carrier (DSB-TC), double-sideband with suppressed carrier (DSB-SC), and transposed modulation] were evaluated. The results showed that DSB-TC and transposed speech were more intelligible than DSB-SC speech, and transposed speech was closer than the other types of BCU speech to air-conducted speech in terms of sound quality. These results provide useful information for further development of the BCUHA. (C) 2012 The Japan Society of Applied Physics

The notion that sound is a normal part of product operation is widespread in society. As a result, much attention has been directed at designing various sounds that are generally treated as noise. Car drivers detect variations in sound characteristics between different buttons, such as the pitch, tone color, loudness and duration of button sounds, and these can affect the desirability of both a car and its audio system. In this study, we focused on the sound design of transient signals and evaluated this design using 11 different button sounds. We examined the subjective evaluations of the sounds by the subjects using the semantic differential method and neuronal activity in their auditory cortices evoked by these stimuli using magnetoencephalography. We found that button sound characteristics significantly affect subjective impressions and neuronal activity in the auditory cortex. ICIC International © 2012.

Because speech signals are easily influenced by noise in the air, speech recognition techniques are not able to achieve a high performance in noisy environments. Consequently, many researchers are investigating speech retrieval/extraction methods in environments where noise reduction or signal extraction methods are used. These methods perform well in high Signal to Noise Ratio (SNR) environments. However, they are not good at measuring speech in low SNR environments such as below 20 dB SNR. Body-conducted speech (BCS) measures signals from a human body with an accelerometer made from magnetic materials, which cannot be used in high magnetic fields such as in a Magnetic Resonance Imaging (MRI) room, where about 80 dB of Sound Pressure Level (SPL) noise exists. For speech communication between a patient and an operator in this environment, we have investigated sound quality improvement of body-conducted speech measured by an Optical Fiber Bragg Grating (OFBG) microphone which is made solely from non-magnetic materials. In this study, we investigated the estimation of clear signals from signals measured by an OFBG microphone using our signal retrieval method. Its effectiveness was proven by time-frequency analysis comparisons with the original signal. ICIC International © 2012.

最重度難聴者が骨導超音波補聴器を用いて音声を知覚できるかどうかを確認するため、最重度難聴者2名を対象に単音節の同定実験を行い、語音明瞭度を測定した。その結果、補聴器から得られる聴覚の手がかりと、読唇で得られる視覚の手がかりの両方を用いると、特定の子音の明瞭度が上がり、結果としてそれぞれ単独の手がかりを用いるより高い明瞭度が得られた。

Continuing the project described by Kato et al. (2009, PASJ, 61, S395), we collected the times of superhump maxima for 51 SU UMa-type dwarf novae, mainly observed during the 2010-2011 season. Although most of the new data for systems with short superhump periods basically confirmed the findings by Kato et al. (ibid.) and Kato et al. (2010, PASJ, 62, 1525), the long-period system GX Cas showed an exceptionally large positive-period derivative. An analysis of public Kepler data of V344 Lyr and V1504 Cyg yielded less-striking stage transitions. In V344 Lyr, there was a prominent secondary component growing during the late stage of superoutbursts, and this component persisted for at least two more cycles of successive normal outbursts. We also investigated the superoutburst of two conspicuous eclipsing objects: HT Cas and the WZ Sge-type object SDSS J080434.20+510349.2. Strong beat phenomena were detected in both objects, and late-stage superhumps in the latter object had an almost constant luminosity during repeated rebrightenings. The WZ Sge-type object SDSS J133941.11+484727.5 showed a phase reversal around the rapid fading from the superoutburst. The object showed a prominent beat phenomenon, even after the end of the superoutburst. A pilot study of superhump amplitudes indicated that the amplitude of superhumps is strongly correlated with the orbital period, and the dependence on the inclination is weak in systems with inclinations smaller than 80 degrees.

Speech is a human instrument for communication, and many applications of speech have been proposed. However, the sound quality of speech is reduced by noise in air, and many researchers and engineers have investigated speech measurement methods in noisy environments in terms of signal processing and the use of noise-robust microphones. Conventional approaches of signal measurement can measure speech in an environment with a high signal-to-noise ratio however, these approaches do not work well in an environment with a low signal-to-noise ratio. By contrast, body-conducted speech, which is speech conducted through the bone and skin of the human body, can be measured in such an environment. However, the frequency characteristics of body-conducted speech are poorer than those of air-conducted speech, and the sound quality needs to be improved for speech applications and conversations. With this background, the paper discusses and investigates sound-quality improvements for the sentence unit of body-conducted speech using differential acceleration, which is a signal retrieval method employed to improve sound quality. The performance of the method is investigated in terms of signal retrieval from body-conducted speech recorded by an accelerometer and Optical Fiber Bragg Grating microphone. © 2012 IEEE.

Ultrasound with a frequency greater than 20 kHz, which is generally recognized as a sound beyond the upper limit of human hearing, can be heard via bone-conduction. Such "audible" ultrasound through bone-conduction is referred to as bone-conducted ultrasound (BCU). It have been reported that profoundly hearing-impaired people can also hear a BCU and recognize part of the information on the modulating signal from the amplitude-modulated BCU. These perceptual characteristics were utilized in the development of a new hearing-aid system, Bone-Conducted Ultrasonic Hearing Aids (BCUHA), for the profoundly hearing-impaired. In this study, to verify the feasibility of "binaural" BCUHAs, we investigated whether listeners can use the interaural time differences in the amplitude envelopes (envelope-ITDs) and the intensity differences (IIDs) as cues for lateralization of BCUs. Results showed that listeners can detect changes in envelope-ITDs or IIDs of BCUs. Also, the discrimination thresholds of the polarities of IIDs were compensated by envelope-ITDs, i.e., the time-intensity trading was observed in the BCU perception. These findings indicate that the auditory system has the ability for lateralization using envelope-ITDs and IIDs of bilaterally presented BCUs. Further, it suggest that bilaterally presented BCUs are processed in the auditory pathway associated with lateralization in a similar manner to high-frequency amplitude-modulated sounds. © 2012 IEEE.

Speech signals are affected by noise, which affects the signal quality, so speech recognition does not perform well in noisy environments. Consequently, many researchers are investigating speech retrieval/extraction methods that use conventional noise reduction methods for noisy speech and other background noise, and signal extraction methods using devices such as microphone arrays. These methods generally work in high signal to noise ratio (SNR) environments. However, they do not work in low SNR environments, typically below -20 dB SNR. In previous research we proposed a body-conducted speech recognition system to measure speech in noisy environments, in which the signal was measured by an accelerometer that was placed on the upper lip. The speech recognition performance achieved was about 95 % when the acoustic model was used to estimate the speech. However, the conventional body-conducted speech microphone is made from magnetic materials, so it cannot be used in high magnetic fields such as in a magnetic resonance imaging (MRI) room, where about 80 dB of sound pressure level noise exists. For communication in an MRI room between an operator and patient, we proposed a new body-conducted speech microphone using an Optical Fiber Bragg Grating (OFBG) microphone, which is made from only non-magnetic materials. In this paper we discuss the estimating of clear body-conducted speech from the OFBG microphone signal with our signal retrieval method, which uses differential acceleration and conventional noise reduction methods. Its effectiveness is proven by time-frequency analysis when it is compared with the non-processed signal from a conventional accelerometer. Copyright © (2011) by the Institute of Noise Control Engineering.

Speech recognition does not perform well in noisy environments. Consequently, researchers are investigating speech retrieval/extraction methods that include noise reduction for noisy speech and other background noise, and signal-extraction methods using devices such as microphone arrays. These methods generally work well in high signal-to-noise ratio (SNR) environments. However, they do not work in low-SNR environments, typically at SNRs below -20 dB. To measure speech in noisy environments, we have previously proposed a body-conducted speech recognition system where the signal is measured by an accelerometer placed on the upper lip. The speech recognition performance achieved was about 95% when an acoustic model was used to estimate the speech. However, a conventional body-conducted speech microphone is made from magnetic materials and thus cannot be used in strong magnetic fields such as those in a magnetic resonance imaging (MRI) room, where the sound pressure level is about 80 dB. For communication in an MRI room between the operator and patient, we proposed a new body-conducted speech microphone using an optical fiber Bragg grating, which is made from only nonmagnetic materials. In this research, we evaluated the effectiveness of the new body-conducted speech microphone in time-frequency analysis. The performance of isolated-word recognition was also evaluated using a speech recognition system with an acoustic model constructed with nonspecific speech.

The focus of production concepts regarding car engine sound has changed in recent years, from finding a solution to noise to designing specific sounds. Although many studies have been conducted to create subjectively pleasant car-engine sounds, the psychoacoustic effects of the accelerating engine sounds are still unclear. The present study investigated auditory impressions of internal car noise using psychological and neurophysiological methods. To represent the half-order sound of an engine, we used harmonic complex tones that simulate acceleration noise with a sinusoidal model as stimuli. Neuronal activity in the auditory cortex evoked by these stimuli were measured using magnetoen- cephalography (MEG). Subjective evaluations were examined using paired-comparison tests. At the same time, we recorded responses in the MEG alpha-wave range (8-13 Hz), and analyzed them using the autocorrelation function (ACF). The results of a jury test confirmed that changes in the level of half-order sound were associated with changes in subjective annoyance, and everyday drivers preferred sound that included a high level of half-order sounds. MEG analyses revealed a relationship between subjective annoyance and the effective duration of the ACF in MEG activity between 8 and 13 Hz.

In recent years, the focus of production concepts regarding car engine sound has changed from finding a solution to noise, to designing specific sounds. Although many studies have been conducted to create subjectively pleasant car-engine sounds, the psychoacoustic effects of the time-varying rate of accelerating engine sounds are still unclear. The present study investigated auditory impressions of internal car noise using psychological and neurophysiological methods. To represent the half-order sound of an engine, we used harmonic complex tones that simulate acceleration noise with a sinusoidal model as stimuli. Neuronal activity in the auditory cortex evoked by these stimuli was measured using magnetoencephalography (MEG). Subjective evaluations were examined using paired-comparison tests. At the same time, we recorded responses in the MEG alpha-wave range (8-13 Hz), and analyzed them using the autocorrelation function (ACF). The results of a jury test confirmed that changes in the level of half-order sound were associated with changes in subjective annoyance, and everyday drivers preferred engine noise that included a high level of half-order sound. MEG analyses revealed a relationship between subjective annoyance and the effective duration of the ACF in MEG activity between 8 and 13 Hz.

「喜び」,「悲しみ」などの特定の感情が込められた音声の聴取時の聴覚初期情報処理過程を明らかにするために,時間分解能と空間分解能に優れた脳磁界計測を用いて検証を行った。計測には1)情動音声認識課題,2)語頭音認識課題 3)音声無視課題の3条件を設定し,1)に関連する初期聴覚情報処理過程の情動処理に関連する潜時を統計的に検定した。その結果,刺激開始後の潜時0.16-0.18sにおいて,右上側頭回後部付近が情動成分への処理に関与していることが示唆された。

The production concept of car engine sound has been changing from finding a solution to noise to designing sound. Although many studies have been conducted on creating comfortable car-engine sound, the psychoacoustic effects of time-varying rate for accelerating-engine sounds are still unclear. Thus, we investigated the effects of increasing the frequency rate of car interior noise on auditory impressions using psychological and neurophysiological methods. Harmonic complex tones that simulate acceleration noise were used as stimuli. First, relationship between'sporty' feeling from dynamic charastics from the engine sound and brain meganetic fields was invertigated. In this investigation, subjective evaluations were examined using the semantic differential (SD) method. And neuronal activities of the auditory cortex evoked by these stimuli were measured by magnetoencephalography (MEG). The results indicated that has a significant effect on subjective impressions and on neuronal activities of the auditory cortex. Second, we investigated the relationships between subjective preference and brain magnetic fields for accelerating car interior noise. Subjective evaluations were examined using the paired-comparison method. At the same time, the MEG alpha-waves range (8-13 Hz) measurements were made and analyzed using the autocorrelation function (ACF). The results indicate that the effective duration of the ACF of the MEGs of between 8 and 13 Hz lengthens after the presentation of a preferred sound.