waveforms to the same amplitude scale the alignment and scaling pre processing step results in two waveforms s 1 and s 2 this preliminary step which corresponds to a simple form of adaptive filtering of the two input waveforms o 1 and o 2 is required in order for the two channel cdcn scheme to perform well a more refined adaptive filtering that would still include the alignment and scaling operations like the adaptive decorrelation filtering outlined in the prior art section for example could be devised instead but it is not a requirement standard cepstral features are computed from each of the aligned and scaled waveforms resulting in the cepstra of the mixed signals x 1 and in the cepstra of the reference signal x 2 box 2 performs the two channel cdcn on the two input streams of cepstra x 1 and x 2 and it outputs the estimated cepstra of the desired speech y 1 fig3 illustrates the principle of the two channel cdcn the goal of the two channel cdcn is to provide an estimate y 1 of the cepstra of the desirable speech signal from the cepstra x 1 of the mixed speech and the cepstra x 2 of the interfering signal assuming that the interfering signal is additive in the waveform domain it is known that the relation between y 1 x 1 and x 2 at each time index t can be written as.