Weighting of interaural time difference and interaural level difference cues in wide-band stimuli with varying low and high frequency energy balance

Abstract

Wideband stimuli carry both interaural time and level difference (ITD and ILD) sound location cues. Previously, listener weighting of those cues has only been measured for low-pass, high-pass, and flat spectrum wide-band conditions [Macpherson and Middlebrooks, JASA (2002)]. In this study, we determined how weighting of ITD and ILD cues varied with the low- and high-frequency energy balance in wide-band stimuli. Listeners reported locations of targets that were presented over headphones using individual head related transfer functions. ITD and ILD cues were manipulated by attenuating or delaying the sound at one ear (by up to 300μs or 10dB), and the final weight was computed by comparing the listener's localization response bias to the imposed cue bias. Stimuli were 100-ms bursts of noise whose spectra were flat from 0.5 to 2 kHz and from 4 to 16 kHz with a level difference between those low- and high-frequency ranges varying in 10-dB steps from −30 to + 30 dB. ILD weight increased (from ~0.5 to 1.5 deg/dB) with increasing high-frequency energy, but ITD weight was constant (~0.08 deg/us) across spectral profiles. The results suggest that in wideband stimuli, weighting of ILD is more stimulus dependent than weighting of ITD.