Daisuke Morikawa

Toyama Prefectural University · Department of Intelligent Robotics

Humans have an amazing ability to monaurally locate sound sources by using various acoustical cues. However, it is not clear how humans can perceive the direction-of-arrival (DOA) of a sound source in three-dimensional (3D) space using monaural acoustic cues. It has been reported that humans can perceive modulation cues in the auditory-localization...

This article describes a linear microphone array used for measuring head-related impulse responses simultaneously at various radial distances using the reciprocal method. The microphone array consists of miniature 5.8 mm diameter electret condenser microphones (ECMs) arranged on a boom, using a 3D printed microphone holder with pillars. The frequen...

Spectral cues (SCs) formed by the pinna are known to be essential for sound externalization, and accurate localization of sound-source azimuth and elevation in binaural listeners. SCs are also know to play a key role in monaural sound localization. The experiments described in this article intended to clarify how changes in SCs associated with head...

The interaural time difference (ITD) plays an important role in spatial hearing, particularly in azimuthal localization of sound images. Although the ITD is essentially determined by the geodesic distance between two ears, researchers have reported that the ITD is greater for lower frequencies. However, the origin of this frequency-dependence has n...

We measured the input impedance characteristics, input voltage versus output sound pressure characteristics, harmonic distortion characteristics, frequency characteristics, and impulse response of a currently available miniature electrodynamic driver unit (Foster Electric, MT006B) when used as a loudspeaker with an open space load. The nominal inpu...

This paper explores the commonalities of the glottal source waves and vocal tract shapes among four speakers in emotional speech (vowel: /a/, neutral, joy, anger, and sadness) based on a source-filter model with the proposed precise estimation scheme. The results are as follows. When compared with the spectral tilts of glottal source waves of neutr...

The movement of a sound image may not coincide with that of the sound source in a room with reflective walls. A listener sitting by a reflective wall perceives the movement of the sound image bending around their head when a sound source approaches the wall straight in the front of them. In order to investigate this perception quantitatively, we me...

In this paper, we clarify the role of variation in interaural level difference (ILD) and interaural time difference (ITD) due to head rotation in localization of spatially segregated sounds. Listeners were asked to distinguish between two sources of white noises having various ILDs/ITDs under head rotation. In ILD condition, the segregation rate re...

This paper investigates the head-related modulation transfer function (HR-MTF) to find out important trends and features for estimating the monaural direction of arrival (DOA). Previous studies suggested that the HR-MTF contains significant trends and features for estimating monaural DOA. However it is still unclear where the range of meaningful mo...

The role of variations in interaural level difference (ILD) and interaural time difference (ITD) due to head rotation in the localization of spatially segregated sounds was investigated by performing listening tests. The participants were asked to distinguish between two sources of white noise having various ILDs/ITDs under head rotation. Under the...

This study investigates acoustic variations when producing Lombard speech under the effect of a changing environment to identify adaptive tendencies of intelligibility. Analyses of the acoustic features of duration, F0, formants, spectral tilts and modulation spectrum in a dataset of speech at noise levels of - ∞, 66, 72, 78, 84, and 90 dB were car...

It is well known that the interaural time difference, interaural level difference and spectral cues are used to determine three-dimensional sound localization in binaural hearing. In the case of monaural hearing, the interaural time difference and interaural level difference are not used. Therefore, it is assumed that there is a different perceptio...

Accurate estimates of glottal source waves and vocal tract shapes can be used for speech synthesis with high quality. One of source-filter models, ARX-LF model, is widely used to estimate glottal source waves of neutral speech and singing voices. This paper extends the ARX-LF model to accurately estimate glottal source waves and vocal tract shapes...

We clarify the role of interaural time difference (ITD) and interaural level difference (ILD) in the localization of spatially segregated sounds. Listeners were asked to distinguish between two sources of white noise having various ITDs/ILDs under head-still and head-rotating conditions. For the former, the segregated rate reached 80% for an ITD of...

Hidden Markov model (HMM)-based synthesized voices are intelligible but not natural especially under limited-data conditions due to over-smoothed speech spectra. Improving naturalness is a critical problem of HMM-based speech synthesis. One solution is to use voice conversion techniques to convert over-smoothed spectra to natural spectra. Although...

HMM-based synthesized voices are intelligible but not natural especially in limited data condition because of oversmoothing speech spectra in time-frequency domain. Improving naturalness is a critical problem of HMM-based speech synthesis. One solution for the problem is using voice conversion techniques to convert over-smoothed spectra to natural...

This study compared the horizontal and median plane sound localization performances of binaural signals provided using a pinna-less dummy head or a stereo microphone that turns in synchronization with a listener's head yaw rotation in the head-still and head-movement tasks. Results show that the sound localization performances in the head-movement...

A TeleHead is a steer able dummy head that tracks a listener's head movement quickly and quietly. We made a personal auditory tele-existence system connecting Toyama Prefectural University and Research Institute of Electrical Communication Tohoku University by using a TeleHead over the Internet. The remote TeleHead can provide dynamic binaural sign...

The effect of listener's voluntary movement on the horizontal sound localization was investigated using a binaural recording/reproduction system with TeleHead, a steerable dummy head. Stimuli were static binaural signals recorded with a still dummy-head in head-still condition, dynamic binaural signals recorded with a dummy-head that followed preci...

We measured subjects' head movements during horizontal and median sound localization experiments in which head-rotation was allowed in order to know how they move their heads to localize sound in a head rotation condition. The head movements in a head-rotation condition were measured while localizing 500-Hz low-pass noise, 12-kHz high-pass noise, a...

Some researchers have reported on how sound localization is affected by the temporal variation of the ITD, ILD and SCs. For horizontal sound localization, Perrett and Noble showed that head rotation facilitated sound localization with 2-kHz low-pass noise. They also showed that head rotation facilitated sound localization with the 2- and 4-kHz high...

This paper clarifies the relationship between head movement and sound localization with band-limited noise (12-kHz high-pass, 500-Hz low-pass and 2-4-, 4-8-, 8-12-kHz band-pass filtered noise). 12-kHz high-pass noise mainly provides interaural level difference (ILD) information, while 500-kHz low-pass noise mainly provides interaural time differenc...

The effects of head movement during head-related transfer function (HRTF) measurements are evaluated. Head movements are measured simultaneously with HRTF measurements and spectral differences of the HRTFs are compared among repeated measurements. Without a head support aid, the human subjects’ heads move considerably in all directions. HRTFs for t...

This paper presents examination of the signal bandwidth necessary to localize real sound sources, and the relationship between bandwidth and the listener's audible frequency range. Horizontal sound localization experiments were conducted with 10 listeners using white noise, high-pass noise with cut off frequencies (Fc) of 2, 4, 8, 12, or 16 kHz, or...

Binaural technology enables the reproduction of the three dimensional (3-D) sound through earphones but requires an acoustically correct sound reproducing system and high-precision individual head-related transfer functions (HRTFs) for spatially distortion-free 3-D sound reproduction. These requirements for the acoustical strictness of binaural sys...

We measured subject's head movements during horizontal sound localization experiments to determine how little the people move their heads in a head-still condition, and how they move their heads in a head-movement condition. The head movements of eight subjects in a head-still condition were measured while localizing six kinds of band-pass noises,...

A study was conducted to clarify the signal bandwidth necessary for horizontal sound localization using high- and low-pass-filtered noise of real sound sources. The experimental system consisted of a Windows-based PC, two 8-channel digital-to-analog converters (DACs), 12 power amplifiers, and 12 loudspeakers. The sampling frequency of the DACs was...

This paper clarifies how much signal bandwidth is necessary for horizontal sound localization. Horizontal sound lo-calization experiments were conducted with sixteen listeners using white noise, and fourteen listeners using high-pass noise whose cut-off frequency (Fc) was 2, 4, 8, 12, or 16 kHz, or low-pass noise whose Fc was 0.5, 1, 2, 4, or 8 kHz...