無限濾波響應之室內聲學廻音消除研究

The Cancellation of Acoustic Echo in Room by using IIR Filtering Response

江煜培(Yu-Pei Jiang)

指導教授 ： 陳國在

國立臺灣大學/工學院/工程科學及海洋工程學研究所/碩士(2005年)

https://doi.org/10.6342/NTU.2005.00118

摘要

摘 要

本文根據數位信號處理技術與適應性主動控制理論，採用無限脈衝響應（IIR）數位濾波器為系統架構，並以Normalized LMS演算法進行系統最佳化運算，用以個人電腦為研發平台，結合圖控式程式語言和類比轉換數位及數位轉換類比信號擷取裝置，建立聲學迴音消除系統。
聲學迴音消除實驗，是以單頻信號與隨機噪音信號輸入由無方向性揚聲器發出聲波，此聲波於迴響室中密閉壁面反射性高環境來進行測試，測試內容包括分析比較不同頻率、參數設定與運算方式，對聲學迴音消除成效之影響，藉以研究其系統性質。
根據實驗結果顯示，單頻信號依頻率高低不同，ERLE可達20至50 dB，而中心頻率迴音衰減量可達60 dB以上；隨機噪音依頻帶高低，ERLE達約2至10，而中心頻率迴音衰減量約為3至15分貝；固定頻寬之隨機噪音，ERLE達約13至18 分貝，而中心頻率迴音衰減量約為10至17 分貝。

關鍵字

適應性主動控制 ； 無限濾波響應

並列摘要

ABSTRACT

Upon the digital signal processing and adaptively active control, this study adopts the (IIR) infinite impulse response digital filter as the systematic structure which combines with the (NLMS) normalized least-mean-square algorithm so as to carry on an optimize operation. To set up the acoustic-echo cancellation system for this study, the combination of the LabVIEW program and A/D-D/A converter data acquisitive equipment with 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 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 ERLE by 20 to 50 decibels for various frequencies form 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 ERLE by 2 to 10 dB or the reduction of centre frequency by 3 to 15 dB is achieved. Moreover, for the case of narrow-band acoustic echo, either the ERLE by 13 to 18 dB or the reduction of centre frequency by 10 to 17 dB is achieved.

並列關鍵字

IIR ； adaptively active control

參考文獻

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