Flexible Beampattern Design Algorithm for Spherical Microphone Arrays

Specific beampatterns of spherical microphone arrays (SMAs) are designed for different noise scenarios. The standard beampattern usually achieves optimum value in one of the performance indicators. Additionally, in acoustics scenarios where positions of several noise sources are known, the beampattern for SMA should be designed to reject signals from noise orientations. This paper presents a flexible beamformer design method for SMA. The beampattern expression is transformed from spherical harmonics expansion to the common polynomial expression, which facilitates the implementation of the standard beampattern and the novel pattern where the zero positions are assigned to reject multiple noise sources. Simulation results reveal that the proposed beamformer shows better flexibility over the high directivity beamformer and Dolph-Chebychev beamformer. The deep-null problem existing in the open-sphere SMA is also discussed and can be mitigated by reducing the radius or increasing the order of the beamformer.