3D Sound Reproduction

Abstract

Psychoacousticians distinguish between a sound source location and an auditory event location. The former is the position of a physical sound source in the listening space, while the latter is the position where a listener experiences the sound [30]. From everyday experience we know that a monophonic audio signal played through a loudspeaker makes the sound source and the auditory event positions coincide. However, it is possible to process the audio signal so that the auditory event occurs at a completely different position in the listening space than the position of the physical loudspeaker emitting the sound. The listener perceives the sound to be coming from the auditory event position, which is, therefore, referred to as a phantom (or virtual) sound source. A simple form of this audio processing is the stereophonic audio system [6], where the amplitude or phase of the sound is panned between two loudspeakers. Stereophonic systems are able to position the auditory event (sound image) at any point on the line connecting the two loudspeakers. A direct extension to this technique is the surround sound system, where more than two loudspeakers surrounding the listener axe used. By panning the sound between every two adjacent loudspeakers, the auditory event can be positioned on lines connecting the loudspeakers [121]. As the number of reproduction loudspeakers increases, the auditory event can be accurately placed at any point in a three-dimensional (3D) space.