Assessment of dynamic spatial release from masking via listener head rotation

Abstract

The dynamic interaural time-difference (ITD) created by listener head rotation is a potent cue for front/rear sound source localization. In principle this cue could also assist in the segregation of simultaneously presented front and rear sources, particularly when robust high-frequency spectral cues are absent. If so, head rotation might provide dynamic spatial release from masking. We assessed this in a spatial auditory attention task in which multiple different equal-intensity sequences of four spoken digits, low-pass filtered at 1500 Hz, were presented simultaneously—the target sequence from 0 or 180 deg azimuth and distractors from lateral angles of ±22.5 and/or ± 45 deg relative to the target, but in the opposite hemisphere. On each trial, listeners either fixated towards 0 azimuth or oscillated their heads at ∼0.5 Hz with an amplitude of ∼±40 deg. Listeners reported the target sequence heard. In a majority of listeners, there was no benefit of head motion, and therefore no evidence of dynamic spatial release from masking for these stimuli. These results are consistent with those of Culling [J. Exp. Psych. 26, 1760–1769 (2000)], who found that in tone complexes with components smoothly changing in ITD, opposite movement direction for one component was not an effective segregation cue.