An adaptive filter coefficients adjustment algorithm stable against reference signal power fluctuation available for acoustic echo canceller systems

The ERLE (echo return loss enhancement) iterates greatly up and down, if the adaptive filter coefficients are continuously adjusted in disregard of the reference signal power fluctuation. This paper presents a method of always maintaining the specified ERLE, even when the adjustment is continued in voiceless noise terms. The method is based on the ‘summatìonal’ NLMS (normalized least mean square) algorithm in which the coefficients are updated after the reference signal norm, and the product of the residual echo and the reference signal have been summed up for continuos iterations (a block). The SNLMS algorithm can keep the ERLE at the specified level, if the coefficients are updated after the summed norm has been amounted to a value which was evaluated from a given surrounding noise power.