A new sixth-order Eigenmike® spherical microphone array for spatial sound field recording

Abstract

A new spherical microphone array capable of up to 6-th order spatial sound field recording is described. Spherical microphone array beamforming is normally accomplished by judicially combining multiple acoustic pressure microphones appropriately mounted on the surface of a rigid sphere to form a set of orthonormal spherical harmonic modal beams or “Eigenbeams” (also referred to as Higher-Order-Ambisonics). Eigenbeamformer processing exploits the diffraction and scattering of the incident acoustic waves onto the rigid sphere. General beamformers are then created by properly combining the orthonormal Eigenbeams to form and steer a desired set of beampatterns up to the decomposition order limit. One advantage of using the modal decomposition approach to beamforming is that it is computationally compact, and results in an elegant scalable beamformer architecture. Steering beams formed by the spherical array is accomplished by a computationally simple matrix multiply. Another benefit is that beampatterns formed using spherical array processing maintain their design spatial responses independent of the steering direction. Beampatterns can also be frequency independent. In this talk, we will describe a new 64-element spherical microphone array and associated software capable of up to 6-th order performance, as well as present some real-world measurements.