Measurement of the effects of nonlinearities on the network-based linear acoustic echo cancellation

It is well known that an over-driven loudspeaker would produce a nonlinearity that limits the performance of an acoustic echo canceler (AEC). In contrast, only a handful of studies have been documented on the effect of speech coding nonlinearity on the AEC. This paper investigates the combined effect of both types of nonlinearities in the network-based AEC framework as opposed to when the AEC is performed at the source of echo such as a cellular handset. The simulation results show that while a mild saturation-type loudspeaker nonlinearity causes the echo return loss enhancement (ERLE) to go down significantly, it is the nonlinear speech coding distortion on the acoustic echo signal that ultimately reduces the achievable ERLE. The results also point to the fact that a low bit-rate speech codec is capable of synthesizing a perceptually acceptable speech signal but does it in a way that is untractable by traditional linear AEC algorithms.