An improved deviation measure for two-path echo cancellation

Abstract

Parallel adaptive filters have been proposed for echo cancellation to solve the dead-lock problem, occurring when the echo is detected as near-end speech after a severe echo-path change; causing the updating of the adaptive filter to halt. To control the parallel filters and monitor their performance, estimates of the filter deviation (i.e. the squared norm of the filter mismatch vector) are typically used.This paper presents a modification of a filter mismatch estimator. The proposed modification requires slightly more computational resources than the original measure, but provides a significant improvement in terms of robustness during double-talk. This is shown both analytically and through simulations.

A Delay-Based Double-Talk Detector

“…As in [12], it can be argued that |ρ D (k)| < |ρ(k)| should hold in most cases since the auto-correlation for speech decreases as the lag increases. For D < 0 this is trivial to realize by comparing equations (14) and (17).…”

“…Further, if any of the signals x(k) and v(k) are white, then ρ(k) = 0. In the case of speech, the magnitude of the first factor in equation (14) is likely to decrease as i increases, since the autocorrelation of a speech signal usually decrease rapidly as the lag increases [12], [13], [14]. Further, since all eigenvalues if X i are non-negative and ≤ 1, the magnitude of the eigenvalues of the matrix resulting of the product i−1 j=0 X j are monotonically decreasing as i increases.…”

“…The detection statistic proposed in this paper is based on the same idea as in [12], where a delay is introduced to reduce the influence of near-end disturbance in a filter deviation measure, although in this paper the idea is used in a DTD context. The proposed detection statistic is…”

“…In practice, r xy , r ye and σ 2 y can be estimated using a running average over a time-window [5], [11] or exponential recursive weighting [9], [12] aŝ…”

Robust low-complexity transfer logic for two-path echo cancellation

“…filter deviation measure presented in [4] and the delay based double-talk detector presented in [5]. A more efficient way of calculating the delay based measures than in the original papers is also presented.…”