(a) Absolute HRTF magnitude (left ear) and (b) interaural phase delay errors, averaged across 110 directions in an approximate Lebedev grid. HRTFs were preprocessed with the nine methods at N = 3 and interpolated. The horizontal dotted lines indicate an approximation of the just noticeable differences: 1 dB for magnitude and 20 μs for phase delay. The vertical dashed line indicates the aliasing frequency.