Evaluating the principal spectral components positioning a virtual sound source on a cone of confusion

Abstract

Although many studies have attempted to identify spectral cues to sound-source direction for the entire sphere of possible incidence angles, few studies have focused their attention on directional hearing for virtual sources positioned on cones of confusion. These regions of space, defined by relatively constant interaural time and intensity differences, provide an ideal subset of incidence angles for testing the importance of the spectral cues to direction allowing for up/down and front/rear distinctions between sources at constant angular distance from the median plane. In this study, head-related transfer functions (HRTFs) measured on a well-lateralized cone of confusion were decomposed into principal spectral components putatively responsible for positioning a virtual sound source, and their related angle-dependent scores that describe the relative contribution of each shape to the total spectral variation. The findings can be summarized as follows: For the set of ipsilateral HRTFs the most significant set of scores shows sinusoidal variation with angle, and could potentially encode a front-back cue, though with the extrema rotated by about 30 deg. The most significant score from an analysis of interaural spectral differences seems to capture a head-shadowing effect which is most extreme in the lower rear.