Measured and theoretical performance comparison of a co-centred rigid and open spherical microphone array

We present a comparison of the measured and theoretical performance of a 64 microphone spherical array. The array has 32 microphones mounted on an open sphere and 32 microphones mounted on a smaller rigid sphere. The two spheres are mounted to be co-centred. Analyses show that this configuration optimises the useable frequency range when beamforming to a constant third order. We have measured the signal-to-noise ratio (SNR) of the constructed co- centred rigid and open spherical microphone array and shown that it matches its theoretical performance of greater than 30 dB SNR across its useable frequency range of 900 Hz to 16.0 kHz. Measurement of the directivity patterns at various frequencies for the third-order spherical beamformer are presented and are shown to closely match the theoretical third-order directivity pattern.