Temporal weighting of interaural time and level differences carried by broadband noises

Localization of real sounds involves integrating acoustic spatial cues as they evolve over time. This study measured binaural sensitivity over time, in the form of temporal weighting functions (TWFs) for trains of of noise bursts. Each stimulus comprised sixteen 1-ms bursts of white noise, presented at an interval (ICI) of 2 or 5 ms. In separate conditions, noise samples were either repeated (“frozen”) or newly generated (“fresh”) across bursts. On each of many trials, listeners indicated the apparent lateral position of a stimulus along a horizontal scale displayed on a touch-sensitive device. Lateral positions varied across trials as interaural time (ITD) and level (ILD) differences ranged +/-500 µs ITD or +/-5 dB ILD. Interaural differences of individual bursts in each train received additional random variation (ranging +/-100 µs and +/-2 dB) to allow calculation of TWFs by multiple linear regression of normalized responses onto per-burst ITD and ILD values. Consistent with past studies, TWFs for “frozen” noise-burst trains demonstrated large ICI-dependent weights on the initial burst (“onset dominance”), elevated weights near offset, and lower weights for interior bursts. Flatter TWFs, smaller onset/offset weights, and greater interior weights were measured for “fresh” vs “frozen” noise burst trains. [Supported by R01 DC011548.]