Practical Aspects of the Calibration of Spherical Microphone Arrays

Spherical microphone arrays have been widely studied for acoustic scene analysis and beamforming. Spatial sound field analysis typically requires two distinct steps: A calibration stage equalizes spatio-temporal deviations of the microphones. Then a decoupling stage extracts orthogonal spatial components of the wave field. For spherical microphone arrays, the decomposition of the measured sound pressure into spherical harmonics has been shown to be a powerful framework, which allows plane wave decomposition analytically in the spherical wave spectrum [1]. The term modal (or sometimes phase mode) beamforming has been coined in literature. However, the approach usually requires an ideal sensor geometry, exact microphone placement and pre-equalization.