Real-Time Implementation of an Acoustic Echo Canceller on DSP

| Acoustic echo cancellation is an essential signal enhancement tool for teleconferencing applications such as hands-free telephony, tele-classing and video-conferencing. However, loudspeaker signals are picked up by a microphone and are fed back to the correspondent, resulting in an unde-sired echo. Nowadays, adaptive ltering techniques are typically employed to suppress this echo. In acoustic applications long lters need to be adapted for suucient echo suppression. Classical adaptation schemes such as LMS are too expensive to do an accurate echo path modelling in highly reverberating environments. Cheaper algorithms were proposed and are mainly based on subband and frequency-domain techniques. However, due to nonlinearities and the time-dependence of the echo path some residual echo will always remain. Apart from the adaptive lter also some post-processing and a steering algorithm have to be included to remove the residuals and to ensure proper operation during double-talk. By modelling then only a part of the echo path more expensive adap-tive algorithms such as LMS can be reconsidered. Diierent adaptive algorithms have been implemented in real time on DSP. They are compared based on a cost/performance analysis. A steering algorithm is used that can withstand the non-stationarities of the acoustic environment.