Model for the interaural time differences in the azimuthal plane

Abstract

An objective study of the steady-state interaural time difference (ITD) was performed on a manikin comprised of a head and torso. Data were taken for both a bare and clothed torso. The measured ITD’s correspond reasonably accurately at the low and the high frequencies to the computed theoretical values for a rigid sphere of an effective radius a. The theoretical ratio of the low-frequency (<500 Hz) ITD to the high-frequency (≳2000 Hz) ITD is 3/2. The measured ITD is a minimum between 1.4 and 1.6 kHz for angles of incidence, ϑinc, of sound between 15° and 60°. At both the low and the high frequencies the data can be expressed by universal curves when the ITD is normalized by (a/c0) sinϑinc, where c0 is the speed of sound in air and ϑinc is the angle of incidence. Both the steady-state ITD and the interaural sound-pressure-level difference (ILD) show differences between measurements made with the bare torso and those with a clothed torso. These objectives results support the subjective measurements of past experiments, which showed that in man there was no localization improvement below approximately 500 Hz, poor localization between 1000 and 2000 Hz, and a change in the localization cue around 1400 Hz from ITD to ILD.