ABSTRACT
One of the most useful applications of adaptive filtering is the method of adaptive noise cancellation (ANC). ANC is concerned with the enhancement of noise corrupted signals. Its great strength is that in contrast to other enhancement techniques no a priori knowledge of signal or noise is required for the method to be applied. In particular, noise cancelling is a variation of optimal filtering which is designed to use a secondary or reference input. The ANC method is based on the principle of adaptively filtering this reference input to produce a replica of the noise which can then be subtracted from the primary measurement. A moments thought, however, will confirm that they are equivalent with the desired input replaced by the primary, and the system input replaced by the reference. It should also be noted that in this application it is the error signal which is the system output.
