Ear Centering for Near-Distance Head-Related Transfer Functions

The head-related transfer functions (HRTF) are a major tool in spatial sound technology for personal use. They are linear filters describing the transmission of sound from a point in space to the ears. The HRTFs are typically obtained for a sparse set of points at a single far distance, from which datapoints at near distances are synthesized using the spherical Fourier transform (SFT) and distance-varying filters (DVF). Ear centering is further required to match the center of the SFT (the center of the head) and the measurement positions (the ears). Hitherto, plane-wave (PW) translation operators have yield effective ear centering when synthesizing HRTFs at far distances. We propose to use spherical-wave (SW) translation operators for ear centering when synthesizing HRTFs at near distances. We contrasted the performance of SW and PW ear centering. Synthesis errors decreased consistently when applying SW ear centering and the enhancement was observed up to the maximum frequency determined by the input far-distance dataset.