An adaptive close-talking microphone array

Close-talking differential microphone arrays (CTMAs) are useful in situations where the background noise level is very high because they inherently suppress farfield noise while emphasizing desired nearfield signals. One problem, however, is that the array has to be placed as close to the desired source (talker's mouth) as possible since the frequency response and level of a differential nearfield array depend heavily on its position and orientation relative to the source signal. In order to be able to utilize the advantages of CTMAs for an extended range of microphone positions, this contribution examines the possibility of tracking the desired signal source by estimating its distance and orientation angle. Having this information, appropriate correction filters can be applied adaptively which equalize unwanted frequency response and level deviations within a reasonable range of operation without significantly degrading the noise canceling properties of differential arrays. A PC-based real-time implementation with transducer calibration capabilities of this adaptive CTMA is presented.