A novel interpolation method of HRTFs based on the common-acoustical-pole and zero model

For control of sound localization, synthesis of Head-Related Transfer Functions (HRTFs) is an important technique. Because HRTFs vary as a function of source location and show large inter-subject variation, systems based on HRTF synthesis should have HRTFs for each listener covering the entire area around the listener. However, it is not practical to obtain them through measurement. One possible solution to this problem is to interpolate measured HRTFs to obtain those for intermediate directions. This study investigates a new interpolation method based on an effective modeling method of HRTFs called the Common-Acoustical-Pole and Zero (CAPZ) model. This model represents measured HRTFs with poles, which are assumed to be independent of all source directions, and zeros, which depend on the source direction. Interpolation of HRTFs is achieved by interpolating MA coefficients corresponding to the zeros. Results show that the proposed method can reduce the necessary data size for a set of HRTFs while retaining the same accuracy as those obtained with conventional methods that use linear interpolation of the impulse responses and magnitude responses. Under the conditions reported in this paper, the data size was reduced to about 30% of the data size obtained with conventional methods.