Effect of transducer mismatch on the performance of spherical microphone arrays

ABSTRACT Spherical microphone arrays(SMAs) were widely used in sound field recording, beamforming,etc. for its advantage of high geometrical symmetry. Many factors could affect the performance of SMAs, including transducer errors. In this paper, effect of transducer mismatch in amplitude and phase on the performance of SMAs was studied through simulation calculation. A SMAs with 64 nearly uniformly distributed transducers was used in the simulation. Beam patterns with and without transducer mismatch errors were calculated, and then the differences between those patterns were compared using beam pattern correlation coefficients as the metric. The simulation and anlyasis results show that under the condition that the spherical harmonics expansion order is not larger than ka(the product of wave number and array radius), the correlation coefficient is not less than 0.97 when the max random transducer amplitude error is less than 3dB or the maximum random transducer phase error is less than 10 degree. This result indicates that the performance of SMAs has a good tolerance to transducer mismatch errors when spherical harmonics truncation order is not larger than ka. While ka less than truncation order, great errors occur due to low-frequency boost nature of SMAs signal processing.