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Performance Evaluation of a Modified Subband Noise Cancellation System in a Noisy Environment

This paper presents a subband noise canceller with reduced residual noise. The canceller is developed by modifying and optimizing an existing multirate filter bank that is used to improve the performance of a conventional full-band adaptive filtering. The proposed system is aimed to overcome problems of slow asymptotic convergence and high residual noise incorporating with the use of oversampled filter banks for acoustic noise cancellation applications. Analysis and synthesis filters are optimized for minimum amplitude distortion. The proposed scheme offers a simplified structure that without employing cross adaptive filters or stop band filters reduces the effect of coloured components near the band edges in the frequency response of the analysis filters. Issues of increasing convergence speed and decreasing the residual noise at the system output are addressed. Performance under white and coloured environments is evaluated in terms of mean square error MSE performance. Fast initial convergence was obtained with this modification. Also a decrease in the amount of residual noise by approximately 10dB compared to an equivalent subband model without modification was reachable under actual speech and background noise.