| Résumé |
Applications using HRTFs or other directivity functions are often combined with interpolation techniques because measurements are only available at discrete directions with finite angular spacing. Linear interpolation, how- ever, creates interference at high frequencies where the phase differences between the measurements are large due to time-delays. For HRTFs, interference is typically minimized by removing the all-pass components and sep- arately interpolating the minimum-phase parts and the time-shifts (linear phase). To preserve the all-pass com- ponents, more general strategies linearly interpolate mag- nitude and unwrapped phase separately in the frequency domain. The unwrapped phase is related to the inte- grated group delay; thus interpolation is performed on group delay and magnitude separately, which seems suit- able for HRTFs. However, spectral phase unwrapping is often degraded by error propagation along the frequency axis when applied to real measurements. We present an alternative solution based on spatial phase unwrapping for each frequency, i.e. unwrapping of the phase across the spherical grid of directional measure- ment data. |
