雙工音場回音消除

Abstract

本篇論文首先針對視訊會議中的音訊通話系統做了封閉迴路之分析, 並與 一般開放迴路之分析結果做比較. 其中包括回音消除器係數之訓練,以及 封閉迴路之回音衰減指數 (ERLE) 的討論. 封閉迴路不穩定產生之原因與 防止方法亦在討論之列. 本篇論文介紹了數種同時對講 (double 之檢測 方法, 並對它們的優缺點加以探討. 亦將針對分辨同時對講及房間脈衝響 應變分, 提出改進之建議. 論文最後提出一回音消除的方法. 此法運用了 一對互差濾波器. 在此結構下, 便不必做係數的訓練與同時對講的檢測. 對於以上的討論分析, 將以電腦模擬驗證之. This thesis focuses on closed-loop analysis of duplex acoustic echo cancellation (DAEC) with applications to teleconference and speaker-phone. Adaptation process and closed-loop ERLE are discussed. The causes and prevention of the closed-loop are also discussed. Several double talk detection methods are introduced and their advantages and drawbacks are discussed. An improved method to distinguish double-talk conditions from room impulse response variation is suggested. In the final part of this thesis, a novel acoustic echo cancellation method using a pair of complementary filters is proposed. In this nonadaptive scheme, training coefficients of filter and double talk detection are no longer needed. Computer simulations are provided under different schemes of DAEC's.