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(11) | EP 0 357 402 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Sound imaging method and apparatus |
| (57) The illusion of distinct sound sources distributed throughout the three-dimensional
space containing the listener is possible using only conventional stereo playback
equipment by processing monaural sound signals prior to playback on two spaced-apart
transducers. A plurality of such processed signals corresponding to different sound
source positions may be mixed using conventional techniques without disturbing the
positions of the individual images. Although two loudspeakers are required the sound
produced is not conventional stereo, however, each channel of a left/right stereo
signal can be separately processed according to the invention and then combined for
playback. The sound processing involves dividing each monaural or single channel signal
into two signals and then adjusting the differential phase and amplitude of the two
channel signals on a frequency dependent basis in accordance with an empirically derived
transfer function that has a specific phase and amplitude adjustment for each predetermined
frequency interval over the audio spectrum. Each transfer function is empirically
derived to relate to a different sound source location and by providing a number of
different transfer functions and selecting them accordingly the sound source can be
made to appear to move. |