Gradient Based Adaptive Filter Algorithm for Single Channel Acoustic Echo Cancellation in Noise

Conventional adaptive echo cancellation schemes are generally suitable for dual channel communication system and their performance degrades significantly in the presence of noise. This paper deals with a challenging task of cancelling both echo and noise in a single channel communication system. In this regard, first, a gradient based single channel adaptive least mean sqares (LMS) algorithm is developed to reduce the effect of echo. Next a spectral subtraction based single channel noise cancellation scheme is employed to reduce the effect of noise and residual echo. In order to overcome the problem of availability of a separate reference signal in single channel communication system, the delayed version of the echo and noise suppressed signal is used as the reference to the proposed adaptive filter algorithm. It is shown that the resulting update equation converges to the optimum Wiener-Hopf solution Several speech signals corrupted by both echo and noise have been tested and it is found that the proposed scheme not only provides an excellent echo cancellation performance in terms of average echo return loss enhancement, but also provides significant improvement in overall signal to distortion ratio.