Decorrelation of input signals for stereophonic acoustic echo cancellation using the class of perceptual equivalence

In communication systems using stereophonic signals, the high correlation of input signals decreases dramatically the behavior of acoustic echo cancelers (AEC´s) especially the misalignment between the estimated impulse response and the real impulse response of receiving room. In this paper, we focus on the decorrelation of input signals without any modification of auditive quality. Using perceptual properties, we show that it is possible to find a set of signals which are perceptually equivalent to input signals, in spite of their different spectral and temporal shapes. Hence, the `class of perceptual equivalence´ (CPE) is defined. It is an interval build in the frequency domain limited by two bounds: the upper bound of perceptual equivalence (UBPE) and the lower bound of perceptual equivalence (LBPE). These two bounds are used as perceptual transparent non linear transformations of input signals in order to decorrelate them. We show experimentally that the improvements yielded by this method are higher than those of classical non linear transformations.