Microphone array beamformer processing to reduce noise and reverberation
* Presenting author
Hands-free audio communication systems that are designed to allow audio and speech communication between remote parties are known to be sensitive to room reverberation and noise, especially when the source is distant from the microphone. One solutionis to use an array of microphones to spatially filter the acoustic field so that the direct sound field from the talker is emphasized while reverberation and background noise is attenuated. It is well known that the maximum directional gain for an array of microphones is N^2 where N is the number of microphones. The maximum microphone array gain is only attainable with specific microphone geometries.Typical gains obtained with realizable microphone arrays are lower than this maximum and the loss can be significant. To increase the direct-to-reverberant ratio in a diffuse field by 20 dB a classical delay-sum beamformer (maximum directional gain of N) would need on the order of 100 microphones. Two algorithms are described that attempt to address the slow growth in directional gain as the number of microphones increase by replacing the standard linear microphone array beamformer with a parametric nonlinear multiplicative processing beamformer that uses multiple overlapping and non-overlapping beamformers to suppress noise and reverberation.