Re-evaluation of the stereo reproduction method using six speakers for media space development

The stereo sound reproduction method using two speakers, positioned to the right and left, is the current standard of audio systems. A user can experience a virtual sound image from the speakers when he or she is midway between them, thus enjoying a rich acoustic scene. However, this sound image can significantly shift and is often fixed to one of the speaker locations due to several audiological phenomena such as the precedence effect. The conventional stereo approach is thus clearly not adequate for application to a video conference site or modern computer-supported media space where an object such as a speaking person is expected to be reproduced acoustically and visually in the correct direction. To overcome this problem, we elaborate a sound reproduction method using six speakers even for two-channel stereo reproduction. Through systematic experiments, we show that the method has a certain effect of widening the usable listening area but that, on the other hand, it is not sufficient even for the use in the traditional video conference site. Extensive analyses of the relation between the time delay and the listening test results suggest that an effective sound pressure control should be integrated with the time delay control, both in the sound collection stage and in the sound reproduction stage.