Morning Tutorial 3

Acoustic echo and noise control belongs to the most challenging signal processing problems. High order adaptive filters are involved. To control their performance sophisticated estimation procedures have to be employed. To enable echo and noise control devices to enter consumer products implementations on low cost signal processing hardware are required.

The tutorial will cover the entire range of problems involved from the modeling of a loudspeaker-enclosure-microphone system (LEMS) to the 16-bit fixed-point implementation with minimized processing demands.

Topics of the tutorial are (e.g.):

• Physical properties of a LEMS
• Modeling a LEMS
• Physical properties of speech signals and noise
• Adaptive algorithms applied for acoustic echo cancelling
• Methods to improve convergence of adaptive algorithms in speech environments
• Methods to reduce computational complexity
• Noise reduction methods
• Coping with ITU and ETSI recommendations
• A speech communication terminal (SCT) moving in a state space
• Estimation of the states of a SCT
• Developing a common hierarchical control of the echo and noise controlling subsystems of a SCT
• Characteristics of implemented systems
• Full-band system
• Sub-band system

Audio examples will be used during the tutorial.

Participants of the tutorial will receive copies of the material used.

Dr. Hänsler received his degrees (Dipl.-Ing., 1961, Dr.-Ing., 1968) in Electrical Engineering from Darmstadt University of Technology, Darmstadt, Germany. He worked with the Research Institute of the German PTT (1961 - 1963), the Electrical Engineering Department of Darmstadt University of Technology (1963 - 1968) and with the IBM Research Division at Zurich and Yorktown Heights (1968 - 1974). Since 1974 he is Full Professor for Signal Theory at Darmstadt University of Technology.

His research interests are signal and system theory, adaptive systems, digital signal processing, echo cancellation and noise reduction. He has been working on the hands-free telephone problem for several years. He is co-founder of the biannual International Workshop on Acoustic Echo and Noise Control (IWAENC), he organized sessions on this topic at several international conferences and acted as guest editor of a Special Issue on Acoustic Echo and Noise Control of Signal Processing in January 1998.

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Last Update:  February 4, 1999         Ingo Höntsch