The main hypothesis behind the perceptual assimilation model (PAM) is that listeners perceive non-native speech sounds based on articulatory similarities between the non-native speech sounds and native speech sounds. When non-native and native sounds are substantially similar, non-native sounds are perceived as equivalent to native ones. Former research shows that the schwa vowel is perceptually assimilated to Japanese /a/ almost exclusively. In this study, we investigate acoustical cues that Japanese listeners rely on to assess the articulatory similarities between the English schwa and the Japanese vowels during the perceptual assimilation. Traditionally, the first two formants (F1 and F2) are considered to be effective for assimilation judgements; however, former investigations imply that these dimensions may be insufficient. In this study, we compared the schwa and the five Japanese vowels in the dimensions of vowel openness and backness using additional information, i.e., the third formant (F3) and fundamental frequencies (F0). The results of the analyses suggest that Japanese listeners use F1, F2, F3 and F0 information to assess articulatory similarities between the schwa and the Japanese vowels during perceptual assimilation.

A conventional sound field synthesis re-creates a highly accurate 3D sound space. However, it is difficult to present spatial sound to multiple listeners because an impractical number of loudspeakers is required for a single synthesized field to cover them all. The present research introduces a new approach, termed ``shared sound field synthesis,'' to multi-zone reproduction, which allows multiple users to simultaneously listen to the spatial sound corresponding to a single sound field. The proposed method considers a new kind of multi-zone transfer function in the spherical harmonic domain to characterize the output of each loudspeaker in the reproduction array. These are calculated using a phase compensation formula to account for sound propagation between zones. Numerical simulations show that the proposed method can consistently achieve a two-zone reproduction with a consistent distortion level below -6 dB and is stable with respect to the relative position between the listening zones, except when the zones and target source are aligned. The size of the low distortion is similar to that of the single-zone synthesis obtained through high-order Ambisonics. Moreover, the proposed method dose not proved significant coloration at low frequency or near the center of the listening zones.

This study deals with development of a high-frequency measurement method of normal-incidence sound absorption coefficient in a cylindrical impedance tube. The authors have previously proposed the method using multiple microphones which enables the normal-incidence absorption coefficient measurement in the frequency range beyond the cut-on frequencies of the higher order acoustic modes. It is confirmed that the proposed method is valid for commonly used absorbing materials at which the scattering does not occur. However, it is difficult to judge whether the scattering occurs or not, only from measured absorption coefficient. Hence, in this study, a method that evaluates the effect of the scattering is proposed to confirm the reliability of the measured results. As an indicator of the scattering effects, a normal-incidence (1, 0)-mode-reflection coefficient and a total power reflection coefficient in a tube are defined. They are derived from the difference between the signals of the two microphones placed on opposite sides of the tube. Numerical simulations were conducted to prove the theory. Finally, the experimental results are shown, confirming the validity and the feasibility of the proposed method.

To realize three-dimensional sound reproduction using a bone-conducted sound reproduction device, the effect of the contact condition between the actuator of the bone-conducted device and the surface of each part of the face on the sound localization performance of binaural sound signals reproduced by the device via bone conduction was investigated. As a result of a subjective evaluation experiment, it was found that the sound localization performance of bone-conducted binaural sound was increased owing to the contact force and position of the actuator device.

This paper investigates the relationship between the effects of auditory and visual stimuli on the distance perception between the subjects themselves and the sound sources. As the auditory stimuli, the effect of the male speech voices and the binaural room impulse responses on the distance perception are comparatively investigated. The relative error of the estimated distances in various audiovisual conditions are discussed. It was found that the subjective impression of the distance to the sound source was effected by both the auditory and visual information, however the extent of the distance perception varied depending on the time variant characteristics of the reproduced sounds.