How to deal with Forbidden frequency in HOA

Question

I notice that resonance audio envelope the listener by HOA, I am curious about how do you deal with forbiden frequency (non-uniqueness) in HOA?

Answer 1

HOA describes sound fields accurately only up to a certain frequency and only within a limited region. This is because the spherical Bessel functions only vanish for small wavenumber * radius values. For higher values, indeed, they can be null and the sound field reconstruction will suffer from spatial aliasing errors.

To deal with this problem, I think it is a common practice to apply frequency-dependent smoothing functions in the spherical harmonics domain. For example, instead of trying to reconstruct a high-frequency sound field, we can apply 'MaxRe' weighting factors to form a different kind of an ambisonic 'panner', which will assure best energy concentration in the direction of the virtual source.