Behavioral and neural sensitivity to changes in large interaural level differences: Implications for sound localization

Sound localization acuity depends on source azimuth: minimum audible angles (MAAs) are smallest for sources near the frontal midline. The azimuthal dependence of MAAs can be partially accounted for by the decreasing rate of change in the acoustic cues to sound location (interaural time and level differences [ITDs and ILDs]) with increasing azimuth. Previous work has shown that changes in low-frequency MAAs across azimuth are well-accounted for by changes in physical ITD alone. Here we consider whether acoustical constraints are sufficient to account for the azimuthal dependence of MAAs for high-frequency tones, which are localized on the basis of ILDs. Psychophysical data were obtained from human subjects tested in two different headphone ILD tasks (discrimination and lateralization) and compared to previously published measurements of psychophysical MAAs and acoustical ILDs across azimuth. We conclude that acoustic factors alone are not sufficient to account for the azimuthal dependence of high-frequency...