The Study of Acoustic Echo Cancellation in Reverberant Enclosure
Date Issued
2005
Date
2005
Author(s)
Lin, Ta-Chun
DOI
zh-TW
Abstract
The interrupt resulting from the acoustic echo exist in some situations dealing with the communication products and audio systems such as telephone, cellphone, hand–free telephone, stereos, hearing aids and headset etc. Among those products, two important acoustic components such as loudspeaker and microphone are included. When the two acoustic components as described are placed in an enclosure or placed too close to avoid the propagation of acoustic energy from speaker to microphone, the acoustic echo to be produced will influence the communication quality, or further causes an uncomfortable hearing to happen.
Upon the adaptively active control theory and the digital signal processing technique, this study adopts the finite impulse response digital filter as the system structure. Regarding to the optimum operation for the control system, a normalized least-mean-square algorithm is selected as well. To further set up the acoustic-echo cancellation system for this study, the combination of an A/D-D/A converter data acquisitive equipment with some personal computer is used as the required platform.
For the experiment of the acoustic-echo cancellation, an enclosure with highly reflective walls is used as the experimental site, and the selected input signals are both of pure-tones and random. The system performances are identified by comparing the methods to set up the parameter of system, its operation performance and their influence on the effectiveness of echo cancellation for various frequencies.
Experimental results show that the averaged ERLE by 20 to 50 decibels for various frequencies from low to high pure-tone sounds are reached. The reductions of echo power spectrum by more than 60 decibels are reached. As regards to the case of randomly acoustic echo, either the averaged ERLE by 2 to 10 dB or the reduction of power spectrum by 3 to 10 dB is achieved. Moreover, for the case of narrow-band of acoustic echo, the reduction by more than 10 to 15 dB of averaged ERLE and power spectrum are achieved.
Subjects
聲學迴音消除
適應性控制
Acoustic echo cancellation
Adaptive control
SDGs
Type
thesis
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