Jingyuan Liu

Publication Date

1994

Document Type

Dissertation/Thesis

First Advisor

Tahernezhadi, Mansour

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Electrical Engineering

LCSH

Teleconferencing--Equipment and supplies; Echo; Noise control--Equipment and supplies

Abstract

In teleconferencing, the use of a speaker-phone system has a troublesome problem associated with it — the acoustic echo. Traditionally, acoustic echoes have been reduced by a very high order adaptive filter to compensate for the long delay of the acoustic echo path. Such a long length adaptive filter results in a high computational complexity and slow convergence of the canceler, making it very difficult to implement in real time. Recently, multirate techniques have been introduced to overcome these difficulties by adapting several shorter filters in subbands at a reduced rate. However, the down sampling process introduces aliasing version of the original signals, especially when signals are critically decimated. A novel subband acoustic echo canceler is proposed to combat the above problems. The new canceler employs non-overlapping main filter banks with decimated auxiliary subbands to alleviate distortion due to aliasing as well as spectral gaps, while the computational simplicity is maintained. The new canceler is implemented in TMS320C30 by both SPOX and assembly language. The real-time and simulation results confirm that the new canceler is both practical and successful. The basic ideas and concepts of multirate signal processing are also included and several filter bank design techniques are discussed in this thesis.

Comments

Includes bibliographical references (pages [122]-126)

Extent

126 pages

Language

eng

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

Media Type

Text

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