The role of high frequencies in speech localization

This study measured the accuracy with which human listeners can localize spoken words. A broadband (300 Hz-16 kHz) corpus of monosyllabic words was created and presented to listeners using a virtual auditory environment. Localization was examined for 76 locations on a sphere surrounding the listener. Experiment 1 showed that low-pass filtering the speech sounds at 8 kHz degraded performance, causing an increase in polar angle errors associated with the cone of confusion. In experiment 2 it was found that performance in fact varied systematically with the level of the signal above 8 kHz. Although the lower frequencies (below 8 kHz) are known to be sufficient for accurate speech recognition in most situations, these results demonstrate that natural speech contains information between 8 and 16 kHz that is essential for accurate localization.