Application of adaptive noise cancellation to noise reduction in audio signals

The LMS adaptive noise cancellation algorithm has been applied to the removal of high-level white noise from audio signals. Simulations and actual acoustically recorded signals have been processed successfully, with excellent agreement between the results obtained from simulations and the results obtained with acoustically produced data. A study of the filter length required in order to achieve a desired noise reduction level in a hard-walled room is presented. The performance of the algorithm in this application is described and required modifications are suggested. A multichannel processing scheme is presented which allows the adaptive filter to converge at independent rates in different frequency bands. This is shown to be of particular use when the interfering noise is not white. Careful implementation of the scheme allows the problem to be broken into several smaller ones which can be handled by independent processors, thus allowing longer filter lengths to be processed in real time.