Differential Beamforming with Null Constraints for Spherical Microphone Arrays

Differential microphone arrays (DMAs) can measure both the acoustic pressure field and the differential acoustic pressure fields, which gives them great advantages in a wide range of applications for acoustic and speech signal acquisition. The core component of DMAs is the so-called differential beamformer, the design of which typically involves taking into account the a priori knowledge about the array geometry and the desired directivity pattern that is related to the differential sound field to respond. This paper deals with the design of differential beamformers with spherical microphone arrays. It presents a novel design approach based on the null constraints formed from the desired directivity pattern. In comparison with the exiting methods, the proposed approach only requires the information of the zeros in the beampattern, which provides notable flexibility and convenience for spherical DMA design in practical applications.