Spectral modification of Head-Related Transfer Functions for improved virtual sound spatialization

Head-Related Transfer Functions (HRTFs) are commonly used to impose a virtual location of origin to mono-aural digital sounds. In listening tests, however, subjects tend to confuse the virtual location of sounds from the front hemisphere with symmetric locations in the back hemisphere, and vice versa, in an effect called “Cone of Confusion”. Preliminary observations suggested that the HRTFs of individuals with particularly protruding ears show more accentuated spectral differences between symmetric locations. When these HRTFs were used for the spatialization of sounds in listening tests performed by other subjects, the cone of confusion effect decreased. This paper describes how to synthesize attenuation/amplification profiles based on those seen in HRTFs from protruding ears and how they are applied to modify the HRTFs of several subjects. Listening tests showed that the HRTFs so modified yielded enhanced front-back differentiation, with respect to the original HRTFs of the test subjects.