Simulations of sound wave flow in conventional stereo - hearing enhancements from center speaker channel in surround sound
N. Subramaniam · 2005
Conventional Hi-Fi Stereo Sound provides lacalization emulating sources in the space between the speakers. Here, a 2-Dim depiction of the sound fields produced by 2 line sources is considered. Above fresuencies of 4 - 5 lrHz , the space standing-wave pattem caused by interference between the two sound sources exhibits distances between null values approaching transverse dimensions of an adult human head (12 - 15 cm). The phase-front is largely elliptical, whilst the singIe center speaker has a circular phase-front (& wavefront) with no standing-wave (SW) characteristics. This frequency range coincides with the well-known sudden improvement in direction perception [ 1 ] ; however, the rapidly changing characteristics of the space SW pattem with frequency cause significant phase distortion in binaural hearing. In surround sound, the common timedomain components of the 2-channel signals would be reproduced in the center-speaker. The voice signals would be reproduced from the center source (of appropriate characteristics) with high directionality & much improved clarity. In typical listening-rooms , the walls cause varying amounts of reflection. Such enclosures enhance the listening pleasure, mainly because human hearing systems are conditioned for such environments. The single-frequency analysis of SW pattems has been measured and analyzed [2.5.6 ] , eg using Geometrical Acoustics (G.A.) indicate large SW pattem distributions. It is proposed that for such cases, the listener (ie his head & body) can cause significant dissolution of the sound fields around him causing SW sound intensity variations to be largely reduced.