Nonlinear Echo Cancellation for Hands-free Speakerphones

Nonlinearities in the amplifier and loudspeaker of hands-free speakerphones limit the performance of linear adaptive acoustic echo cancellers, necessitating the use of nonlinear cancellation schemes. A nonlinear acoustic echo canceller based on the WienerHammerstein model structure of a cascade of linear, memoryless nonlinear, and linear elements is proposed. By modeling the true structure of the nonlinear system, the proposed canceller requires relatively few adaptive parameters, offering significantly lower storage and computational requirements than more general nonlinear adaptive filtering techniques. Experimental results on measured loudspeaker signals indicate that the proposed nonlinear echo canceller provides as much as an 8.4 dB improvement in Echo Return Loss Enhancement (ERLE) over a linear Normalized LMS canceller with little additional computation.