Directional Resolution of Head-Related Transfer Functions Required in Binaural Synthesis
In binaural synthesis a virtual sound source is implemented by convolving an anechoic signal with a pair of head-related transfer functions (HRTFs). In order to represent all possible directions of the sound source with respect to the listener a discrete number of HRTFs are measured and interpolations are made in between. A listening experiment was done to estimate the lowest directional resolution with which HRTFs have to be measured to ensure that interpolations between them do not introduce audible errors. In order to make this study the HRTFs of an artificial head were measured with a directional resolution of 2°. The measurements were used to create HRTF data sets with low resolution from which interpolations were made in the horizontal, frontal, and median planes. Measured and interpolated HRTFs were compared in a three-alternative forced-choice listening experiment for both stationary and moving sound sources. A criterion was found that predicts the experimental results. This criterion was used to estimate the directional resolution required in binaural synthesis for all directions on the sphere around the head.
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