The dominant role of low-frequency interaural time differences in sound localization

TLDR

Simulations that preserve directional cues produce virtual source directions that closely match real free‑field sources. The study investigates how listeners judge the apparent directions of headphone‑presented virtual sound sources designed to simulate free‑field conditions. The experiments manipulate interaural phase relations in the processing algorithms to generate stimuli where interaural time difference cues indicate one direction while interaural intensity and pinna cues indicate another. When low frequencies are present, listeners’ perceived directions follow the interaural time cue; removing low frequencies eliminates this dominance, causing perceived direction to be governed by interaural intensity difference and pinna cues.

Abstract

Two experiments are described in which listeners judge the apparent directions of virtual sound sources–headphone-presented sounds that are processed in order to simulate free-field sounds. Previous results suggest that when the cues to sound direction are preserved by the simulation, the apparent directions of virtual sources are nearly the same as the apparent directions of real free-field sources. In the experiments reported here, the interaural phase relations in the processing algorithms are manipulated in order to produce stimuli in which the interaural time difference cues signal one direction and interaural intensity and pinna cues signal another direction. The apparent directions of these conflicting cue stimuli almost always follow the interaural time cue, as long as the wideband stimuli include low frequencies. With low frequencies removed from the stimuli, the dominance of interaural time difference disappears, and apparent direction is determined primarily by interaural intensity difference and pinna cues.