Accounting quantitatively for sensitivity to envelope-based interaural temporal disparities at high frequencies

Bernstein and Trahiotis [(2009). J. Acoust. Soc. Am. 125, 3234-3242] reported threshold interaural temporal disparities (ITDs) conveyed by the envelopes of 4-kHz-centered "raised-sine" stimuli. A raised-sine stimulus consists of a carrier modulated by a sinusoid raised to an exponent. Such stimuli permitted Bernstein and Trahiotis to vary, independently, stimulus modulation frequency, modulation depth, and "relative peakedness/deadtime." An interaural correlation-based model that included stages mimicking peripheral auditory processing captured most of the data save for an overestimation of threshold ITDs obtained when the depth of modulation was 25% and the raised-sine exponent was 8.0. The purpose of the present study was: (1) to present a quantitative evaluation of how well other measures, including normalized envelope fourth moment, envelope peakwidth, and envelope "deadtime" might also account for the data reported by Bernstein and Trahiotis and (2) to present new threshold ITDs measured while varying, factorially, depth of modulation, raised-sine exponent, and modulation frequency. Quantitative analyses of both the prior and the new data showed that the normalized interaural correlation, computed subsequent to peripheral auditory processing, provided the most accurate predictions. Importantly, the overestimation of threshold ITDs did not occur when it was assumed that listeners can employ information within "off-frequency" auditory filters. (C) 2010 Acoustical Society of America. [DOI: 10.1121/1.3466877]