Tap-length optimization of adaptive filters used in stereophonic acoustic echo cancellation

Abstract

An adaptive filter with a large number of weights or taps is necessary for stereophonic acoustic echocancellation (SAEC), depending on the room impulse response and acoustic path where the cancellationis performed. However, a large tap-length results in slow convergence and increases the complexity ofthe tapped delay line structure for FIR adaptive filters. To overcome this problem, there is a need for anoptimum tap-length-estimation algorithm that provides better convergence for the adaptive filters usedin SAEC. This paper presents a solution to the problem of balancing convergence and steady-state performanceof long length adaptive filters used for SAEC by proposing a new tap-length-optimization algorithm.The optimum tap length and step size of the adaptive filter are derived considering an impulseresponse with an exponentially-decaying envelope, which models a wide range of acoustic echo paths.The tap-length optimization is applied to a single long adaptive filter with thousands of coefficients todecrease the total number of weights, which in turn reduces the computational load. To further increasethe convergence rate, the proposed tap-length-optimization algorithm is applied to an existing multiplesub-filter-based echo canceller, for which we present a convergence analysis. Computer simulations arealso presented, comparing the proposed approach with related work