Temporal effects in interaural and sequential level difference perception.

Abstract

Temporal effects in interaural level difference (ILD) perception are not well understood. While it is often assumed that ILD sensitivity is independent of the temporal stimulus properties, a reduction of ILD sensitivity for stimuli with a high modulation rate has been reported (known under the term binaural adaptation). Experiment 1 compared ILD thresholds and sequential-level-difference (SLD) thresholds using 300-ms bandpass-filtered pulse trains (centered at 4 kHz) with rates of 100, 400, and 800 pulses per second (pps). In contrast to the SLD thresholds, ILD thresholds were elevated at 800 pps, consistent with literature data that had previously been attributed to binaural adaptation. Experiment 2 showed better ILD sensitivity for pulse trains than for pure tones, suggesting that amplitude modulation enhances ILD sensitivity. The present ILD data and binaural adaptation data from the literature were predicted by a model combining well-established auditory periphery front-ends with an interaural comparison stage. The model also accounted for other published ILD data, including target ILD thresholds in diotic forward and backward fringes and ILD thresholds with different amounts of interaural correlation. Overall, a variety of temporal effects in ILD perception, including binaural adaptation, appear to be largely attributable to monaural peripheral auditory processing.