Low Complexity -nlms Algorithms and Subband Structures for Stereophonic Acoustic Echo Cancellation

FOR STEREOPHONIC ACOUSTIC ECHO CANCELLATION Tetsuya Hoya, Jonathon A. Chambers, and Patrick A. Naylor Communications and Signal Processing Group, Department of Electrical and Electronic Engineering, Imperial College of Science, Technology, and Medicine, University of London SW7 2BT, U.K. e-mail: [email protected] ABSTRACT One of the fundamental problems in Stereophonic Acoustic Echo Cancellation (SAEC) lies in the misadjustment in the lter coe cients due to the two strongly correlated channel-inputs. In this paper, we study the e ect of the normalisation factor, , within the twochannel NLMS ( -NLMS) algorithm for subband SAEC and show that the optimal choice may be close to the variance of the channel-input data. In the simulation study with real speech datasets, it is observed that subband stereo echo cancellers using the Fast Least Squares (FLS) algorithm in lower bands and the -NLMS algorithm, with the optimal normalisation factor setting, in higher frequency bands can improve misalignment performance signi cantly compared with using only the FLS algorithm in all subbands. In addition, around 23dB further misalignment performance improvement is obtained by applying smoothly time-varying allpass lters in the lower frequency bands, while introducing no perceptible auditory degradation.