Extent of lateralization caused by interaural time differences of high-frequency click-trains

Abstract

Hafter and Dye [J. Acoust. Soc. Am. 73, 644 (1983)] measured threshold interaural time differences (ITDs) for high-frequency click-trains. They found that, given a fixed duration, threshold ITDs were better (lower) for lower pulse rates. Studies by other authors measured lateralization for broad band click-trains and were generally not focused on how the low-frequency fine-structure ITD may influence the results. Such an influence may become prominent at ITDs > 600 μs when fine-structure ITDs alone are subject to a cue reversal. The current study therefore focused on high-frequency click-trains and a broad range of ITDs (up to at least 2 ms). The extent of lateralization elicited by these click-trains was determined using an acoustic pointer procedure. Interclick intervals of 5, 10, 20, and 50 ms were investigated. Subjects show an increase in lateralization with increasing ITD even when exceeding the physiologically plausible range of 600 μs. Inter-click intervals of 5 ms generally cause the lowest extent of lateralization, in line with the threshold ITD data. The results will be discussed in the light of spatial cue enhancement for cochlear implants, assuming a similar extent of lateralization for interaural pulse time differences at low pulse rates.