Dominance of head-motion-coupled directional cues over other cues during walking depends upon source spectrum

Listeners who walk past a continuously presented speech sound source emanating from a fixed spatial position will typically experience veridical perception of source location. If, however, walking listeners are fitted with binaural hearing instruments that allows for the signals reaching their ears to be interchanged, left for right and right for left, the sound source is typically reported to be located in a spatial region that is reversed with respect to all three spatial axes: left for right, front for back, and above for below. This result has been taken as evidence for the relative dominance of dynamic interaural directional cues over the spectral directional cues associated with each listener’s own pinnae which should support veridical perception. In order to investigate the relative importance of the spectral energy distribution of the source on the illusory reversals of source location, bursts of broadband noise were presented rather than continuous speech. Under these circumstances, with greater energy in higher frequency bands, the reversals did not readily occur. Therefore, it has been concluded that head-motion-coupled directional cues are likely to dominate spectral cues associated with the filtering effects of the listener’s pinnae only for sources containing greater energy at lower frequencies.