Combining beamforming methods and antenna rotation for sound sources localization with a spherical microphone array

A 16-microphones spherical array is used to localize and identify reflections in room acoustics. By increasing the number of microphones on the array, the spatial resolution is expected to be improved, but at the expense of cost and complexity. In this study, the number of microphone positions is rather increased by sequentially rotating the spherical array around its vertical axis. We show how to combine the microphone signals measured at different positions of the rotating table to increase the order of beamforming and obtain better spatial resolutions. In particular,
four optimized azimuthal positions are defined and tested with three beamforming methods: PWD, DAS and MVDR. The method combining beamforming and antenna rotation is first tested with synthetic plane waves at different frequencies. The results of sound source localization are compared with the ones obtained with the original 16 microphone positions. It is shown that some improvements are obtained in the spatial resolution, depending on the frequency and the beamforming method. The combination method is then tested with real sound fields. Theoretical results are retrieved for 16 and 64 microphone positions.