ADAPTIVE MICROPHONE ARRAY

The present invention is directed to a method of apparatus of enhancing the signal-to-noise ratio of a microphone array. The array includes a plurality of microphones and has a directivity pattern which is adjustable based on one or mo re parameters. The parameters are evaluated so as to realize an angular orientation of a directivity pattern null. This angular orientation of the directivity pattern nu ll reduces microphone array output signal level. Parameter evaluation is performed under a constraint that the null be located within a predetermined region of spa ce. Advantageously, the predetermined region of space is a region from which undesir ed acoustic energy is expected to impinge upon the array, and the angular orientati on of a directivity pattern null substantially aligns with the angular orientation of undesired acoustic energy. Output signals of the array microphones are modified based on one or more evaluated parameters. An array output signal is formed base d on modified and unmodified microphone output signals. The evaluation of parameters, the modification of output signals, and the formation of an array ou tput signal may be performed a plurality of times to obtain an adaptive array respons e. Embodiments of the invention include those having a plurality of directivity pat terns corresponding to a plurality of frequency subbands. Illustratively, the array ma y comprise a plurality of cardioid sensors.