Abstract:
Spatial hearing research suggests that the most salient of the acoustical cues which determine the apparent position of a sound image are the interaural difference in time-of-arrival of the sound at a listener's two ears and the filtering of the sound by the listener's pinnae. An accurate virtual auditory space can be created by assuring that each sound source present in the space produces, at the listener's eardrums, the interaural delay and spectral cues appropriate to the intended position of the sound. If headphones are used to produce the sounds, synthesis of a virtual source can be accomplished by convolving the source signal with a left--right pair of filter impulse responses. Each filter includes a delay, a pinna filter that is appropriate to the desired source position, and compensation for the headphone characteristics. The fidelity of the resulting virtual auditory space depends critically on the similarity of the pinna filters used in the synthesis and the listener's own pinna filters. A currently available wireless consumer 3-D audio device incorporates listener matched pinna filters to render Dolby surround sound over headphones. Thus, the user hears sound from five locations exactly as if listening to a conventional home-theater system.