A method for continuing adjustment of adaptive filter coefficients in voiceless noise terms available for acoustic echo canceller systems

Abstract

AbstractIn the acoustic echo canceller, the speaker input signal is used as a reference signal to update adaptive filter coefficients, and is sometimes composed of only the far‐end background noise.This paper proposes a configuration in which the estimation error is kept constant also for a voiceless noise period, while continuously updating the coefficients. the summational normalization LMS is used as the adaptive algorithm, where the products of the residual echo and the transmitted signal (i.e., the numerators of the coefficient update resulting from the normalized least mean square (NLMS) algorithm), as well as the norm of the transmitted signal (i.e., the denominator of the forementioned), are accumulated, respectively, for a certain number, and the ratio of the two sums is used as the coefficient update.The summation number is controlled by the power of the transmitted signal. When, for example, the configuration is such that the coefficients are updated only when the sum of the norms reaches a certain value (i.e., the threshold), the echo cancellation is maintained at the desired value, independently of the power of the transmitted signal. the cancellation is enhanced in the period where the power of the transmitted signal is increased. In addition to the control method, which can calculate the power of the environmental noise needed in determining the threshold, this paper analyzes the structure of the filter.