Auditory distance perception in rooms

The perceived distance of a sound source in a room has been shown to depend on the ratio of the energies of direct and reflected sound(1). Although th is relationship was verified in later studies(2-4), the research has never led to a quantitative model. The advent of techniques for the generation of virtual sound sources(5,6) has made it possible to study distance percepti on using controlled, deterministic stimuli. Here we present two experiments that make use of such stimuli and we show that a simple model, based on a modified direct-to-reverberant energy ratio, can accurately predict the res ults and also provide an explanation for the 'auditory horizon' in distance perception. The modification of the ratio consists of the use of an integr ation time of 6 milliseconds in the calculation of the energy of the direct sound. This time constant seems to be important in spatial hearing-the pre cedence effect is also based on a similar integration window(7).