5th European Conference on Speech Communication and Technology

Rhodes, Greece
September 22-25, 1997

Subband Echo Cancellation in Automatic Speech Dialog Systems

Andrej Miksic, Bogomir Horvat

Laboratory for Digital Signal Processing Faculty of Electrical Engineering and Computer Science, University of Maribor, Maribor, Slovenia

Echo cancellation has been most widely studied for hands-free telephony and for cancelling line echos in telephone central offices. The problem of echo cancelling in speech dialog systems is similar, however it has some specific requirements. In this contribution, a subband echo cancellation structure is proposed which can be integrated in the feature extraction part of a recognizer. A NLMS gradient-based adaptation is performed in frequency subbands that can either be derived directly from FFT analysis of input speech signal, or by using a proposed reduced-subband approach where the number of subbands is reduced in order to lessen the aliasing effect of the FFT. A double-talk detector is proposed based on the estimated error function for decision on stopping the adaptation. Finally, a new approach of combining echo cancellation and noise reduction is proposed.

Full Paper

Bibliographic reference.  Miksic, Andrej / Horvat, Bogomir (1997): "Subband echo cancellation in automatic speech dialog systems", In EUROSPEECH-1997, 2579-2582.