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DECOUPLED SECOND-ORDER VOLTERRA FILTER STRUCTURE USING THE NLMF ADAPTIVE ALGORITHM FOR NONLINEAR ACOUSTIC ECHO CANCELLATION

The paper proposes a nonlinear acoustic echo cancellation setup based on a decoupled scheme of the second-order adaptive Volterra filter. The acoustic distortions that take place in the Loudspeaker-Enclosure-Microphone setup are modeled using measured linear and quadratic Volterra kernels. The adaptation of the filter weights is achieved by exploiting the Normalized Least-Mean-Fourth algorithm. The proposed method is compared with the usual direct adaptation procedure of the second-order Volterra filter using the same algorithm and the same step size values. Comparisons between these techniques regard the evolution of the Echo Return Loss Enhancement in terms of convergence rate and steady-state error. Experimental results for Laplacian distributed excitation show that the new approach increases the speed of convergence in comparison to the one given by the coupled version without enhancing the steady-state error.