Abstract
Sound localization studies over the past century have predominantly been concerned with directional accuracy for far-field sources. Few studies have examined the condition of near-field sources and distance perception. The current study concerns localization and pointing accuracy by examining source positions in the peripersonal space, specifically those associated with a typical tabletop surface. Accuracy is studied with respect to the reporting hand (dominant or secondary) for auditory sources. Results show no effect on the reporting hand with azimuthal errors increasing equally for the most extreme source positions. Distance errors show a consistent compression toward the center of the reporting area. A second evaluation is carried out comparing auditory and visual stimuli to examine any bias in reporting protocol or biomechanical difficulties. No common bias error was observed between auditory and visual stimuli indicating that reporting errors were not due to biomechanical limitations in the pointing task. A final evaluation compares real auditory sources and anechoic condition virtual sources created using binaural rendering. Results showed increased azimuthal errors, with virtual source positions being consistently overestimated to more lateral positions, while no significant distance perception was observed, indicating a deficiency in the binaural rendering condition relative to the real stimuli situation. Various potential reasons for this discrepancy are discussed with several proposals for improving distance perception in peripersonal virtual environments.
Highlights
The basic mechanisms of sound localization have been well studied in the last century
For sources located in the near field, several studies have shown through analysis of proximal-region Head-Related Transfer Function (HRTF) measurements a dramatic increase in Interaural Level Difference (ILD) cues for sources within 1 m of a listener’s head for positions away from the median plane
There is a slight increase of Interaural Time Delay (ITD) for nearest distances, it occurs only near the lateral positions where the ITD is large and where listeners are relatively insensitive to ITD changes
Summary
The basic mechanisms of sound localization have been well studied in the last century (see Blauert, 1997). For sources located in the near field, several studies (see Brungart and Rabinowitz, 1999; Shinn-Cunningham et al, 2000) have shown through analysis of proximal-region Head-Related Transfer Function (HRTF) measurements a dramatic increase in Interaural Level Difference (ILD) cues for sources within 1 m of a listener’s head for positions away from the median plane. This increase is the consequence of two factors. This creates an acoustic parallax effect that laterally shifts some of the high-frequency features of the HRTF (see Brungart, 1999)
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