Noise cancellation using parallel adaptive filters

The development of adaptive noise cancellers based on the reference microphone approach proposed by B. Widrow et al. (1975) is presented. It is shown that the use of multiple reference microphones improves the performance of noise cancelers in a multipath, multisource noise environment commonly found in an automobile. Cancellation based on subbands of the reference signals and the structure of the canceler are shown to improve the ability of the canceler to track nonstationary noise processes. The authors compare various parallel multireference filter structures using noise recorded in an automobile to show that a two-stage canceler using a precorrelation stage followed by a beamforming stage provides noise reduction at all frequencies in the telephone audio band with a maximum reduction of 28 dB and an average reduction of 16 dB