The Far-Field Equatorial Array for Binaural Rendering

Abstract

We present a method for obtaining a spherical harmonic representation of a sound field based on a microphone array along the equator of a rigid spherical scatterer. The two-dimensional plane wave decomposition of the incoming sound field is computed from the microphone signals. The influence of the scatterer is removed under the assumption of distant sound sources, and the result is converted to a spherical harmonic (SH) representation, which in turn can be rendered binaurally. The approach requires an order of magnitude fewer microphones compared to conventional spherical arrays that operate at the same SH order at the expense of not being able to accurately represent non-horizontally-propagating sound fields. Although the scattering removal is not perfect at high frequencies at low harmonic orders, numerical evaluation demonstrates the effectiveness of the approach.

Spherical Harmonic Decomposition of a Sound Field Using Microphones on a Circumferential Contour Around a Non-Spherical Baffle

“…We observed this in [20] where we proposed an earlier EMA solution in which the scattering due to the array baffle was approximated rather than modeled accurately. The inaccuracies of this approximation produced a massive low-frequency boost for sources closer than, say, 1 m. The sound fields due to close sound sources do indeed violate the assumption of height invariance that underlies EMAs and eXMAs.…”

“…The EMA was proposed in [14], which is a generalization of the solution from [20]. An EMA is essentially an SMA as described in Sec.…”