Nobuo Koizumi
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Featured researches published by Nobuo Koizumi.
Presence: Teleoperators & Virtual Environments | 1994
Shigeaki Aoki; Michael Cohen; Nobuo Koizumi
A technique is presented for dynamically invoking a set of head-related transfer functions (HRTFs) and scaling gain, driven by a dynamic map in a graphic window. With such an interface, users may configure a virtual conferencing environment, manipulating virtual positions of teleconferees. The design of a personal headphone teleconferencing prototype is proposed, integrating spatialized sound presentation with individualized HRTF measurement using a bifunctional transducer. According to judgment tests, the use of individualized HRTFs instead of dummy-head HRTFs can reduce front-back sound image confusion.
Presence: Teleoperators & Virtual Environments | 1998
Michael Cohen; Nobuo Koizumi
Audio windowing is a front-end, or user interface, to an audio system with a real-time spatial sound back end. Complementing directionalization by a digital signal processor (DSP), gain adjustment is used to control the volume of the various mixels ([sound] mixing elements). Virtual gain can be synthesized from components derived from collective iconic size, mutual distance, orientation and directivity, and selectively enabled according to room-wise partitioning of sources across sinks. This paper describes a derivation of virtual gain, and outlines the deployment of these expressions in an audio windowing system.
international conference on acoustics, speech, and signal processing | 1987
Shigeaki Aoki; Nobuo Koizumi
Audio conferencing quality can be improved by introducing the localization effect for participants at both sites. This paper proposes a new method which can expand the listening area with good localization for each participant in audio conferencing. The method can suppress interference between sounds radiated to different listening areas by using the localization-in-head and precedence effects and the directivity of a doublet source. The proposed stereo reproduction system employs three pairs of loudspeakers placed on a rectangular table. The effectiveness of the system is confirmed by subjective testing and its performance with various recording methods is also investigated. It can provide good localization not only at the center of the listening area, but also at its sides. In terms of recording method, using a center-placed microphone with two spaced microphones was found to contribute to good localization.
ieee virtual reality conference | 1993
Michael Cohen; Nobuo Koizumi
Audio windowing is a front-end, or user interface, to an audio system with a spatial sound backend. Besides the directionalization of the DSP spatialization, gain adjustment is used to control the volume of the various sources. Virtual gain can be synthesized from components derived from iconic size, distance, orientation, and directivity, and selectivity enabled according to room-wise partitioning of sources across sinks. The authors describe the mathematical derivation of the calculation of virtual gain, and outlines the deployment of these calculations in an audio windowing system.<<ETX>>
IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences | 1992
Michael Cohen; Nobuo Koizumi
Journal of the Acoustical Society of America | 1990
Shigeaki Aoki; Nobuo Koizumi
Journal of The Audio Engineering Society | 1992
Nobuo Koizumi; Michael Cohen; Shigeaki Aoki
Journal of The Audio Engineering Society | 2002
Akira Nishimura; Nobuo Koizumi
Journal of The Audio Engineering Society | 2003
Akira Nishimura; Nobuo Koizumi
ieee virtual reality conference | 2001
Nobuo Koizumi; William L. Martens; Jens Herder