Contribution to the improvement of acoustic echo cancellation systems.

Summary The need for acoustic echo cancellation processing arises when a sound recording picks up a disturbing echo from a loudspeaker broadcasting a sound signal in a room or a vehicle interior. Many books cover the different algorithmic aspects of this discipline. In addition, the different algorithmic options have been widely studied and the evolution of processors now allows the realization of efficient echo cancellers. Since the beginning of the 90's, new applications and the will to realize stereophonic systems restoring a natural communication in videoconference (reproduction of the speakers' position) have oriented the research towards the extension of monophonic processing to the stereophonic case. The new difficulties encountered are essentially due to the sound recording model of this type of application, which generates highly correlated signals whose consequences have been widely exposed. During this thesis, two research axes have been followed: first, to contribute to the improvement of stereophonic echo cancellation methods applied to videoconferencing systems, with a particular interest in the extension of frequency adaptive filtering algorithms to the stereophonic case. This study has opened the way to a new modified frequency algorithm that deals with the correlation of input channels and whose application to videoconferencing systems seems promising. Secondly, to study the implementation of a stereophonic echo cancellation system to deal with the echo of a car radio disturbing a voice recognition system on board a vehicle. This application has only been studied a few times, and the results of the work carried out in this field have notably allowed the realization of a demonstrator, realized for a car manufacturer, allowing the vocal control of the functions of a car radio.