Discrimination of interaural envelope correlation for high- and low-standard correlations

Abstract

This experiment examined the cues that listeners use in discriminating interaural envelope correlation. Thresholds for discriminating normalized interaural envelope correlation [r; see L. R. Bernstein and C. Trahiotis, J. Acoust. Soc. Am. 100, 1754–1763 (1996)] were measured for a sinusoidally amplitude-modulated 4-kHz tone. The parameter r was manipulated by varying the interaural phase difference (IPD) of the signal envelope. Using a method of constant stimuli that measured percent correct, threshold Δr (ΔIPD) was estimated for standard r=1 (IPD=0 deg) and r=0.4235 (IPD=180 deg), with modulation frequencies (fm) of 4–256 Hz and modulation index=0.9. For low fm, thresholds expressed as Δr were from 10–60 times larger for the small standard correlation than for r=1. However, when expressed in terms of difference in the peak interaural level difference (ILD), thresholds were within several dB across standards. Furthermore, thresholds were comparable to those for discrimination of fixed ILDs. For high fm, discrimination thresholds were smaller than those at low fm. The difference at high fm may be due to processing of the interaural envelope differences as fixed interaural time differences rather than dynamically varying ILDs. [Work supported by NIDCD DC00683.]