Contribution of spectral cues to human sound localization

Abstract

The contribution of spectral cues to human sound localization was investigated by removing cues in 12-, 1- or 2-octave bands in the frequency range above 4 kHz. Localization responses were given by placing an acoustic pointer at the same apparent position as a virtual target. The pointer was generated by filtering a 100-ms harmonic complex with equalized head-related transfer functions (HRTFs). Listeners controlled the pointer via a hand-held stick that rotated about a fixed point. In the baseline condition, the target, a 200-ms noise burst, was filtered with the same HRTFs as the pointer. In other conditions, the spectral information within a certain frequency band was removed by replacing the directional transfer function within this band with the average transfer of this band. Analysis of the data showed that removing cues in 12-octave bands did not affect localization, whereas for the 2-octave band correct localization was virtually impossible. The results obtained for the 1-octave bands indicate that up–down cues are located mainly in the 6–12-kHz band, and front–back cues in the 8–16-kHz band. The interindividual spread in response patterns suggests that different listeners use different localization cues. The response patterns in the median plane can be predicted using a model based on spectral comparison of directional transfer functions for target and response directions.