On the ability of human listeners to detect dispersion in head-related transfer functions
Zachary A. Constan, William M. Hartmann · The Journal of the Acoustical Society of America · 2002
Because of dispersion around the head, the interaural time difference (ITD) depends on frequency. However, virtual reality experiments have shown that human listeners cannot distinguish between veridical head-related transfer functions (HRTFs) and HRTFs with a carefully chosen constant ITD. A reasonable explanation for this result is that listeners are insensitive to the kind of dispersion created by the head. This explanation was tested in headphone experiments using incident angles and particular noise bands chosen to give listeners the best opportunity to detect dispersion. The dispersive ITD was modeled using Kuhn’s equations for pressure on a spherical surface due to an incident plane wave [J. Acoust. Soc. Am. 62, 157–167 (1977)]. Listeners were required to distinguish between noise with dispersive ITD and noise with constant ITD. Experiment 1 varied the ITD and found a pronounced minimum in the percentage of correct responses at an optimal value of ITD. Experiment 2 used optimal ITDs only in order to remove lateralization cues. Experiment 3 reversed the sign of the dispersion, causing the ITD to increase with increasing frequency rather than decrease. All experiments led to the same conclusion: listeners cannot detect head-related and similar dispersion. [Work supported by NIDCD.]