Decoupled Loudness and Range Control for a Source Located Within a Small Virtual Acoustic Environment

For headphone-based spatial auditory display systems, binaural synthesis of sound localization cues typically use source reproduction level as the primary control for source range. This approach can be quite effective when indirect sound is simulated in order to externalize virtual sources within a small virtual acoustic environment. A computationally efficient simulation solution is described here that does not rely solely upon the sound reproduction level of the source to control source range (i.e., perceived egocentric distance), and provides an extremely economical synthesis of the indirect sound component that is effective in creating externalized spatial auditory images. The performance of the solution has been psychophysically validated using indirect scaling methods that required experimental listeners to compare two displayed sound stimuli and report which of the two was the louder or the closer. In particular, it was shown that the simulation allows for decoupled loudness and range control for a source located near the listener’s head, so that equally loud sources can be positioned at varying source range. Likewise, within certain limits, source loudness may be varied while holding source range constant. This performance feature has benefits for auditory display applications for which selective attention should be supported for a spatially distributed set of virtual sound sources.