摘要
本論文針對網路電話線路迴音(Line Echo)，提出一迴音消除演算法TD-ARMA (Time Delay-Auto Regressive Moving Average)。其中TD模型用來移除由類比轉數位(Analog to Digital，簡稱A/D)與數位轉類比(Digital to Analog，D/A)裝置所產生的時間延遲，ARMA模型則用來描述電腦電話整合閘道器(Computer Telephony Integration Gateway)中混合電路(Hybrid Circuit)的電子特性。於TD-ARMA演算法中，開迴路搜尋方式求得最佳延遲時間，並使用閉迴路的分析獲得ARMA濾波器中的最佳係數。 實驗結果證實，TD-ARMA對於消除線路迴音有好的表現，且所需計算量與濾波器長度都很小。
並列摘要
The TD-ARMA (Time Delay-Auto Regressive Moving Average) algorithm was proposed to cancel the line echo under the Window-based CTI (Computer Telephony Integration) gateway. The TD model was applied to remove the time delay effect contributed from the A/D and D/A devices. The ARMA model was used to well simulate the electronic properties of hybrid circuit of CTI gateway. In the TD-ARMA algorithm, the opened-loop search method was used to obtain the optimal time delay value and the closed-loop analysis was used to obtain the optimal parameters of ARMA filter. The experimental results confirm that the TD-ADRM has good performance on the line echo cancellation. Moreover, the computational complexity is low and the filter length is small. The VoIP application was also applied to verify the performance of TD-ARMA algorithm. The line echo was removed and the intelligent speech was obtained.