Acoustic echo canceller algorithm based on the variation characteristics of a room impulse response

A NLMS (normalized LMS) adaptive algorithm is proposed for an acoustic echo canceller with double the convergence speed of but the same computational load as the conventional NLMS. This algorithm, called the ES (exponential step) algorithm, implements a different value of step gain (feedback factor) for each tap coefficient of a canceller. These step gains are weighted exponentially along the series by the same exponential ratio as the expected variation in a room impulse response. This algorithm is implemented in a commercial subband echo canceller, and its superiority to the conventional algorithm is demonstrated