1. A method of masking a residual echo signal by an echo canceller, said method comprising: receiving a far-end signal; adjusting filter coefficients of an adaptive filter in response to said far-end signal; generating an echo model signal based on said far-end signal using said adaptive filter; receiving a near-end signal; subtracting said echo model signal from said near-end signal to generate an output signal; defining a spectral mask based on said near-end signal, wherein said spectral mask is indicative of near-end spectral peaks and near-end spectral valleys; de-emphasizing said output signal in spectral regions of said neat-end spectral peaks, using a weighted filter based on medium term spectral characteristics of said near-end signal; and emphasizing said output signal in spectral regions of said near-end spectral valleys.