How can auditory presence be generated and controlled?

Abstract

This paper reviews key results of many listening tests on auditory presence, especially auditory localization (AL) and auditory spatial impression (ASI) by the author. The author gave the first demonstration that AL in any direction can be simulated through two loudspeakers using head-related transfer functions (HRTFs). However, individual differences in HRTFs affect the accuracy of AL. It is basically possible to localize sound images in any direction using median-plane HRTFs combined with interaural differences. Furthermore, HRTFs can be simplified by the combination of only some spectral peaks and notches. Meanwhile, the author demonstrated that ASI comprises at least two perceptual components. One is auditory source width (ASW), defined as the width of a sound image fused temporally and spatially with the direct sound image. The other is listener envelopment (LEV), which is the degree of fullness of sound images around the listener, excluding the sound image composing ASW. A listener can perceive these two components separately. The perception of ASW and LEV has a close connection with the law of the first wavefront. Acoustic components under the upper limit of the law contribute to ASW, and acoustic components beyond the upper limit of the law contribute to LEV.