Control of perceived distance in virtual audio displays

Although virtual audio displays have advanced significantly in the past fifteen years, their ability to provide robust information about the distance of a virtual sound source remains limited. This paper reviews several possible methods for adding distance information to a virtual auditory source. Loudness and spectral cues can provide information about the exocentric, or relative, position of a sound source, but cannot be used to determine the absolute distance of a source without a priori information about its characteristics. Reverberation can provide absolute distance information, but the parameters for controlling perceived distance with reverberation cues are not well defined. One promising technology for adding absolute distance cues to virtual audio displays is based on distance-dependent changes in the interaural intensity difference when the source is near the head. The effectiveness of each of these distance cues is discussed along with issues related to their implementation in virtual audio displays