Objective and subjective evaluation of numerically estimated head‐related transfer functions

Abstract

In this study, head‐related transfer functions (HRTFs) of a dummy head and human subjects are numerically estimated by using the boundary element method (BEM), and their availability for auralization is discussed from the subjective viewpoints. Geometries of their heads are obtained by a 3‐D laser scanner. The effect of the torso for the estimation of the HRTFs is also examined and discussed via the 3‐D measurement. The estimated HRTFs are compared for each subject with the measured HRTFs in various objective criteria, such as spectral distortion (SD), signal‐to‐distortion ratio (SDR), and interaural time/level differences (ITD/ILD). Availability of the estimated HRTFs for the synthesis of the 3‐D sound image are then evaluated via hearing experiments. In our previous study [Proceedings of WESPAC IX (2006)], the results of the experiment is insufficient since the low‐frequency range of the estimated HRTFs caused the ambiguity in sound localization. In this study, the frequency range of the estimation is extended to as high frequency as possible, and the availability of the estimated HRTFs for auralization is discussed from two viewpoints: the subjective difference between the estimated and measured HRTFs, and some subjective attributes obtained from the hearing of the stimuli convoluted with the estimated HRTFs.