MICROPHONE ARRAYS AND BEAM STEERING
Question: Can we improve performance using multiple microphones?

The goal of a microphone array is to localize a sound source by directing a group of microphones to be most sensitive in a specific direction. The procedure is completely analogous to analog antenna theory.

Steering of the array has several uses: increase SNR, direct video in teleconferencing, enhance the human interface (hands-free).

Steering the array amounts to adjusting the delays in each microphone. The most common implementation is the delay and sum beamformer: An example of a sensitivity pattern for this type of array is: A 3D array can be used to localize sound to a single point in a room (direction and distance). 2D arrays are most commonly used to enhance SNR. Unfortunately, performance increases slowly as a function of the number of microphones (1 dB rule). Hence, this technology is impractical for many consumer applications.

Two microphone versions of this idea based on adaptive filtering are popular in automotive applications for noise suppression.