The influence of binaural cues on the promotion or inhibition of auditory stream segregation

Abstract

Though much is known about detection thresholds for binaural cues (interaural time [ITD] and level differences [ILD], and interaural correlation [IAC]), less is known about how these cues influence the separation of auditory sources. The ABA auditory stream segregation paradigm (Bregman, 1990) in a bistable configuration, elicits roughly equivalent proportions of integrated and segregated percepts, where listeners spontaneously switch back and forth between the two. To determine the influence of binaural cues we periodically (25 s) manipulated the binaural cue carried by the A components of the ABA triplet (made of narrowband noise, 6-semitone separation) while maintaining the B component at a stable binaural cue. Participants continuously indicated their perception via button box. Analyzed as a function of binaural cue, lateral cues were more likely to be reported as segregated than midline cues. Binaural cue boundaries (perceptual transition point) were defined using logarithmic regression and were significantly correlated for ILD and ITD (r2 = 0.65, p < 0.05). IAC modulation resulted in significantly more switches when both the A and B components were centered (IAC = 1) than when the IAC of the A component was more diffuse (IAC < 0.9). These results provide evidence of how listeners functionally use binaural cues to segregate auditory streams.