Institute for Data Analysis and Visualization

This paper concerns the use of a simple head-and-torso model to correct deficiencies in the low-frequency behavior of experimentally measured head-related transfer functions (HRTFs). This so-called \snowman'' model consists of a spherical head located above a spherical torso. In addition to providing improved low- frequency response for music reproduction, the model provides the major low-frequency localization cues, including cues for low-elevation as well as high-elevation sources. The model HRTF and the measured HRTF can be easily combined by using the phase response of the model at all frequencies and by \cross-fading'' between the dB magnitude responses of the model and the measurements. For e+-cient implementation, the exact snowman HRTF is approximated by two time delays and two first-order IIR filters. Because the poles are independent of the location of the virtual source, this supports a simple real-time implementation that allows for arbitrarily rapid head and source motion.