6 Beamforming Combined with Multi-channel Acoustic Echo Cancellation

Abstract

For audio signal acquisition, beamforming microphone arrays can be efficiently used for enhancing a desired signal while suppressing interference-plus-noise. For full-duplex communication systems, not only local interferers and noise corrupt the desired signal, but also acoustic echoes of loudspeaker signals. So far, we did not distinguish between local interferers and acoustic echoes. However, for suppressing acoustic echoes, more efficient techniques exist, which exploit the available loudspeaker signals as reference information. These methods are called acoustic echo cancellers (AECs) [SK91, BDH+99, GB00, BH03]. To cancel the acoustic echoes in the sensor channels, replicas of the echo signals are estimated and subtracted from the sensor signals. Acoustic echo cancellation is an application of system identification (Sect. 3.2.1). While the problem of monophonic acoustic echo cancellation has been studied f or many years now, acoustic echo cancellation was only recently extended to more than one reproduction channel [SMH95, BBK03].