Publication Date


Document Type


First Advisor

Kuo, Sen M. (Sen-Maw)

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Electrical Engineering


Telephone--Echo suppresors; Signal processing--Digital techniques; Telephone--Noise


This thesis presents the design and implementation of a full-duplex speaker-phone system. The existing acoustic echo and line echo are reduced by using adaptive filtering techniques. In this study, the system hardware and communication software are presented. An analysis of the closed-loop system is studied to provide insight into the system stability issues. A closed-loop gain controller is designed and implemented. This controller includes the two echo cancelers, voice activated attenuators and speech detectors for proper execution protocol of the system. Furthermore, simulation and real-time experiments and performance of the two echo cancelers are presented and explained. Another major subject of this thesis is the use of multirate digital signal processing techniques in noise cancellation applications. Subband filter theories and designs are explored and are proposed in canceling the broadband noise picked up by the microphone in an acoustic environment. Simulation and real-time experiments are conducted to compare with a full band adaptive noise canceler. Finally, the whole system is integrated with a speaker-phone and tested on the TMS320C5x DSP platform.


Includes bibliographical references (pages [121]-122)


xi, 122 pages




Northern Illinois University

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