An adaptive close-talking microphone array

Directional microphones are best noted for their noise reduction properties in communication systems. Close-talking differential microphones are particularly useful when the noise environment disturbs the ability to communicate without error, such as in public and cellular telephony, aircraft communications, etc. These differential microphones work best when they are spaced within 1 cm from the lips of the talker where the sound field has a large gradient. For a plane-wave sound field, the sensitivity rises proportional to /spl omega//sup n/ where n is the order of the difference. Users of differential microphones do not always correctly position the sensor at the proper distance from the mouth and therefore the sensitivity of the microphone may also rise proportional to /spl omega//sup n/ especially at high frequencies. We describe a method of correcting for this high frequency gain without significantly degrading the noise canceling properties of first and second-order differential microphones.