Nobuo Koizumi

Design and control of shared conferencing environments for audio telecommunication using individually measured hrtfs

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.

Virtual Gain for Audio Windows

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.

Expansion of listening area with good localization in audio conferencing

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.

Virtual gain for audio windows

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>>