Spherical harmonic modal beamforming for an augmented circular microphone array

With the proliferation of inexpensive digital signal processors and high-quality audio codecs, microphone arrays and associated signal processing algorithms are becoming more attractive as a solution to improve audio communication quality. For room audio conferencing, a circular array using modal beamforming is potentially attractive since it allows a single or multiple beams to be steered to any angle in the plane of the array while maintaining a desired beampattern. One potential problem with circular arrays is that they do not allow the designer to have control of the spatial response of the array in directions that are normal to the array. In this paper we propose an augmented circular microphone array that allows one to have some control of the vertical spatial response of the array. A second-order system was built and measured.