Naive performance on interaural time difference discrimination with high-frequency amplitude-modulated tones

Abstract

Humans are sensitive to changes in interaural time differences (ITDs) in high-frequency sounds with fluctuating amplitude envelopes. However, despite noted large individual differences in high-frequency ITD discrimination ability, to date, most investigations of this performance have employed only a few, typically experienced, listeners. Thus, it is not clear whether the data thus obtained are representative of the general, naive, population. Here, ITD discrimination thresholds with high-frequency amplitude-modulated tones were examined in nineteen listeners, all naive to psychoacoustic testing. The large range of performance across these listeners accommodated the collective data previously reported, but was not fully illustrated by any single previous investigation with a small sample size. For these naive listeners, ITD discrimination performance at high frequencies, 1) was much worse than that at low frequencies, 2) was better with a slower (0.15 kHz) than a faster (0.3 kHz) modulation rate with a 4-kHz carrier, and 3) did not differ between a lower (4 kHz) and higher (6 kHz) carrier frequency with a 0.3-kHz modulation rate. These data help establish high-frequency ITD discrimination performance in the general population, and may aid in the interpretation of performance measured in situations where testing time is limited. [Work supported by NIH.]