HRTFs must be stored as large azimuth-elevation tables because interpolation fails.

Evidence

These filter functions can then be used directly to “pan” a monaural source to a particular direction in the binaural stereo perspective. Because it is difficult to interpolate between HRTFs for different angles, these functions have to be stored as a large table of data in both azimuth and elevation. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2250

Categorization

• QUESTION: Why are HRTFs so hard to interpolate between angles — is it pinna notch structure, timing, or something else?