Effect of the Interaural Time Difference on the Loudness of Pure Tones as a Function of the Frequency

Abstract

Significant loudness variations with source azimuth (i.e. directional loudness) are generally accounted for by at-ear pressure modifications. An effect of the interaural time difference (ITD) was also reported in previous studies by the authors: the loudness of pure tones (200 and 400 Hz) significantly increased when the stimuli were presented with an ITD of 772 μs, corresponding to an azimuth of 90°. The present study aims at observing this effect for higher frequencies, including frequencies at which ITD is no longer useful as a localization cue. The effect of ITD on the loudness of pure tones was thus studied at 500, 707, 1000, 1404 and 2000 Hz. Results show that the effect of ITD on loudness is not significant above 500 Hz, even for frequencies where ITD is still a localization cue. The effect observed at 500 Hz is still in agreement with the results reported by previous studies as the loudness of a pure tone significantly increases when its ITD is 772 μs.