Audibility of Differences in Adjacent Head-Related Transfer Functions

The smallest directional change that can reliably be perceived provides a useful measure to assess the required spatial resolution for virtual spatial sound. Here, the ability of naive listeners to discriminate changes in the characteristics of HRTFs was measured. In one experiment the smallest angular separation needed to discriminate between the magnitude spectrum of HRTFs was determined. In a second experiment the smallest change in interaural time difference (ITD) that could just be audible was determined. Generic HRTFs were used for both experiments. Results showed a large inter-subject variability, which was particularly pronounced for discrimination of changes in ITD. Mean thresholds for changes in ITD ranged from 87.8 to 163 μs. Mean thresholds for discrimination of spectral differences ranged from 2.4 to 11°, and significant differences were found depending on the direction of change. Results suggest that ITDs do not seem to require very high resolutions, and that spatial resolution for spectral characteristics is not uniform meaning that different resolutions are needed depending on sound direction.