Differential lateralization interference for interaural time and interaural level differences

Lateralization thresholds were obtained in a 21FC task using 200‐ms noise bands presented with either an interaural time or level difference. The elevation in lateralization threshold (interference) caused by a simultaneously presented noise band was measured. When the ITD was applied to a 50‐Hz‐wide noise band centered at 500 Hz, there was minimal interference from a diotic 400‐Hz‐wide noise band centered at 4000 Hz. When the ITD was applied to the noise band centered at 4000 Hz, there was substantial interference from a diotic band of noise centered at 500 Hz [D. Mcfadden and E. G. Pasanen, J. Acoust. Soc. Am. 59, 634–639 (1976)]. In contrast, the interfering effect of a dioticnoise band was greater when the ILD was applied to the 500‐Hz band of noise than when it was applied to the 4000‐Hz band of noise. A similar pattern of results was obtained when the ITD or ILD of the interfering band of noise was randomized from interval to interval, although randomization produced greater interference in all conditions. The complementary pattern of results for time and level differences favors an explanation based on averaging between simultaneous interaural parameters rather than a masking‐based explanation.