Common-acoustical-pole and zero modeling of head-related transfer functions

Use of a common-acoustical-pole and zero model is proposed for modeling hea d-related transfer functions (HRTF's) for various directions of sound incid ence. The HRTF's are expressed using the common acoustical poles, which do not depend on the source directions, and the zeros, which do, The common ac oustical poles are estimated as they are common to HRTF's for various sourc e directions; the estimated values of the poles agree well with the resonan ce frequencies of the ear canal. Because this model uses only the zeros to express the HRTF variations due to changes in source direction, it requires fewer parameters (the order of the zeros) that depend on the source direct ion than do the conventional all zero or pole/zero models. Furthermore, the proposed model can extract the zeros that are missed in the conventional m odels because of pole-zero cancellation. As a result, the directional depen dence of the zeros can be traced well. Analysis of the zeros for HRTF's on the horizontal plane showed that the nonminimum-phase zero variation was we ll formulated using a simple pinna-reflection model, The common-acoustical- pole and zero (CAPZ) model is thus effective for modeling and analyzing HRT F's.