Lateralization of large interaural delays

Two experiments explored the limits of listeners' abilities to interpret large interaural time delays (ITDs) in terms of laterality. In experiment 1, just-noticeable differences (jnd's) were measured, using an adaptive procedure, for various reference ITDs of Gaussian noise between 0 and 3000 microseconds. The jnd's increased gradually with reference ITD for reference ITDs between 0 microsecond and 700 microseconds, then rose sharply to plateau at much higher jnd's for the remainder of the standard ITDs tested (1000-3000 microseconds). The second experiment tested left/right discrimination of Gaussian noise that was interaurally delayed up to 10,000 microseconds, and high-pass filtered to cutoff frequencies between 0 Hz (broadband) and 3000 Hz. There was good discrimination (62%; significantly above chance, p < 0.05) for broadband and 500-Hz high-pass cutoff stimuli for all ITDs up to 10,000 microseconds, and for ITDs up to at least 3000 microseconds for higher high-pass cutoff frequencies. These results indicate that laterality cues are discriminable at much larger ITDs than are experienced in free-field listening, even in the absence of energy below 3 kHz.