Contrasting monaural and interaural spectral cues for human sound localization

Abstract

A human psychoacoustical experiment is described that investigates the role of the monaural and interaural spectral cues in human sound localization. In particular, it focuses on the relative contribution of the monaural versus the interaural spectral cues towards resolving directions within a cone of confusion (i.e., directions with similar interaural time and level difference cues) in the auditory localization process. Broadband stimuli were presented in virtual space from 76 roughly equidistant locations around the listener. In the experimental conditions, a "false" flat spectrum was presented at the left eardrum. The sound spectrum at the right eardrum was then adjusted so that either the true right monaural spectrum or the true interaural spectrum was preserved. In both cases, the overall interaural time difference and overall interaural level difference were maintained at their natural values. With these virtual sound stimuli, the sound localization performance of four human subjects was examined. The localization performance results indicate that neither the preserved interaural spectral difference cue nor the preserved right monaural spectral cue was sufficient to maintain accurate elevation judgments in the presence of a flat monaural spectrum at the left eardrum. An explanation for the localization results is given in terms of the relative spectral information available for resolving directions within a cone of confusion.

Auditory Spatial Perception: Auditory Localization

“…A number of studies demonstrated that people listening with just one ear can localize sound sources in the horizontal plane although such localization accuracy is much poorer than with two ears and all localization judgments are shifted toward the active ear (Belendiuk and Butler, 1975;Butler 1987;Butler and Flannery, 1980;Jin et al, 2004;Morimoto, 2001;Oldfield and Parker, 1984a;Van Wanrooij and Van Opstal, 2004). Such localization ability is proof that horizontal localization can, to some degree, be facilitated by monaural cues.…”

“…The relative importance of the interaural spectral cues to the localization of sound sources at different elevations is hard to generalize since it varies with the lateral position of the sound source (e.g., Jin et al, 2004). Oldfield and Parker (1986) demonstrated that monaural localization in the vertical plane, which does not take advantage of the interaural spectral cues, is 15 relatively good but somewhat less accurate than binaural localization.…”

Localization Error: Accuracy and Precision of Auditory Localization

“…These effects and reflections produce peaks and troughs in the sound spectrum that are unique for each sound source location in space relative to the position of the listener (Bloom, 1977;Butler & Belendiuk, 1977;Watkins, 1978). Monaural cues and the related Interaural Spectrum Difference (ISD) also help binaural horizontal localization (Jin et al, 2004;Van Wanrooij & Van Opstal, 2004), but they are most critical for vertical localization and front-back differentiation. The spectral cues that are the most important for accurate front-back and up-down differentiation are located in the 4-16 kHz frequency range (e.g., Langendijk & Bronkhorst, 2002).…”

An elevation coding method for auditory displays

“…Previous studies on elevation illusions and elevation localisation used different sound sources, such as noises of different bandwidths, random signals, etc. [5,11,15,16,25], to demonstrate the correlation between the perceived elevation and the frequency centroid of a sound [22,31], i.e. that the sounds with higher pitch appeared to the listener as if originating from higher elevation.…”