Linearly constrained minimum variance method for spherical microphone arrays in a coherent environment

A method for noise reduction and de-reverberation is presented. The method is designed for a spherical microphone array and formulated in the spherical harmonics domain on the basis of an acoustic model that is also formulated in the spherical harmonics domain. The proposed method is suitable for an environment with coherent reflections and requires direction-of-arrival (DOA) estimation of the signal reflections, rather than room impulse response identification. The method is composed of two stages: a multi-output beamformer that decomposes the direct sound and source reflection; and a linearly constrained minimum variance (LCMV) filter designed for noise reduction while avoiding signal-cancellation. The proposed method allows flexibility in design for reverberation reduction, noise reduction and the prevention of signal cancellation. The paper concludes with a simulation that demonstrates the performance improvement obtained by applying the proposed method.