Some observations on sensitivity to HRTF magnitude

The spatial resolution at which head-related transfer functions (HRTFs) are available is an important aspect in the implementation of virtual spatial sound. How close HRTFs must be depends on how much their characteristics differ between adjacent directions and, most important, when these differences become audible. Thresholds for the audibility of differences in the spectral characteristics of HRTFs as a function of angular separation were measured. Listeners had to discriminate between stimuli spectrally shaped with different HRTFs but whose interaural time difference remained the same. Results showed that listeners were more sensitive to changes in the vertical position than to changes in the horizontal position. Results are discussed in connection with requirements for spatial resolution of HRTFs in the synthesis of three-dimensional sound.