Second-order differential adaptive microphone array

An adaptive second-order differential microphone design is proposed here that is constructed from a weighted sum of omnidirectional microphones. Theoretically, only three microphones are required to form a second-order array. The three microphone signals are combined to form three unique fixed second-order beams. Any second-order differential beampattern can be realized using a weighted sum of these three ldquobuilding-blockrdquo beam outputs. If certain simple constraints are placed on the weighting of the three fixed beams, the two null locations that define the final second-order beampattern can be constrained to defined angular regions.