Method for determining the step size Alpha for adjusting the convergence speed in the NLMS algorithm

摘要

The method involves forming a cross-correlation function of two microphone signals in each sampling period, determining an absolute maximum of the function, and evaluating, both an amplitude and a position of the maximum through fuzzy logic. A level comparison of the microphone signals, after a corresponding delay of each signal according to predetermined time constants, is performed, and a respective mean value is formed and filtered. The results of the cross-correlation function and the level comparison are linearly combined in a fuzzy logic, and the resulting signal is filtered in a non-linear low-pass filter. A step-width element is calculated from the resulting signal, and is normalized in dependence on a microphone sum signal, a residual echo, and the result of the level comparison.