Zero-phase signal conditioning for improved NLMS performance

The NLMS algorithm has low computational cost and exhibits optimal performance with excitation by Gaussian noise, but has poor performance with coloured signals such as speech. This paper proposes an acausally-conditioned (AC-NLMS) method for coloured signals which adjusts the correlation matrix governing adaptation behaviour to an LMS approximation of that for Gaussian noise so as to permit near-optimal NLMS performance. The low computational complexity of NLMS is conserved. The technique has potential applications to acoustic echo and noise cancellation.