Abstract: A process and a system for adaptive filtering of a digital telephone signal, in which the digital telephone signal is submitted to a frequency transformation and to a sub-band filtering in order to produce a plurality of sub-band signals. Each of the sub-band signals is submitted in turn to an adaptive filtering starting from a reference signal based on a long-term statistics regarding the telephone signal, equalization by blind deconvolution of the effects of the telephone transmission lines on the digital telephone signal thus being obtained.

Abstract: For equalizing a speech signal constituted by an observed sequence of successive input sound frames, which speech signal is liable to be affected by disturbances, the speech signal is modelled by means of a hidden Markov model and, at each instant t: equalization filters are constituted in association with the paths in the Markov sense at instant t; at least a plurality of the equalization filters are applied to the frames to obtain, at instant t, a plurality of filtered sound frame sequences and an utterance probability for each of the paths respectively associated with the equalization filters applied; the equalization filter corresponding to the most probable path in the Markov sense is selected; and the filtered frame supplied by the selected equalization filter is selected as the equalized frame.