Auditory source width (ASW; the spatial extent of a perceived sound) is a basic aspect of an object’s spatial configuration, yet the specific cues that listeners use to judge ASW remain poorly understood. One feature that does seem to drive ASW judgments is interaural coherence (IAC), i.e., the similarity of waveforms arriving to each ear. Greater IAC tends to be associated with compact images whereas low IAC results in greater ASW, consistent with impacts of diffuse or reverberant sound. Past research suggests the importance of low-frequency IAC cues, i.e., fluctuations of interaural phase difference. Here, we investigated ASW and position judgments for sounds presented stereophonically in the free field while manipulating the coherence of left and right audio channels. Sounds were 100-ms bursts of 0.3 octave bandwidth, centered on 500, 1000, 2000, or 4000 Hz. Component bands were presented singly or in combination. For single narrow bands, we assessed the reliability of judgments across multiple presentations of identical noise tokens. Significant variation in ASW was noted across tokens despite close matching of IAC. Token-level analyses suggest that ASW judgments reflect the specific spectrotemporal dynamics of binaural cues, rather than the long-term or nominal IAC. Work supported by NIH T35-DC008757.
Hopkins-Morand et al. (Wed,) studied this question.