本研究探討圓管中裝置反應式擴張管(Reactive Muffler)配合主動式噪音控制之混合型噪音控制。其中，主動式噪音控制實驗是採用FIR濾波器及配合適應性LMS演算法而實施，分別探討單頻頻率300Hz、500Hz與700Hz 之間，未裝置擴張管之前與裝置之後及配合主動控制的結果來做比較；並且改變擴張管直徑與長度，觀察對各頻率控制結果的變化與影響。由即時控制實驗中已獲致混合控制系統較傳統擴張管或ANC單獨控制更具有消音效果。除此之外，主動式與反應式控制之前後順序亦可影響本混合系統之效果。再者，本文亦針對加裝擴張管後之管內聲場作數學模擬，期能瞭解在本聲場中，擷取參考訊號之最佳位置及其合適性。從模擬與實驗的結果可知，對於主動噪音控制而言；其參考訊號之擷取優劣，影響控制效果甚巨。此外，研究中亦針對本系統之傳輸損失(Transmission Loss)與介入損失(Insertion Loss)作一探討。另外，於ANC系統中，其適應性LMS演算法之階數及步階參數之選取將會影響主動控制之結果，而取樣率更與控制效果關係密切，因此研究中亦對此作電腦模擬控制並逐一探討之，藉此可作為改善主動控制系統之參考依據，使本系統之整體消音效果更理想。最後，在研究中又引入灰色理論，藉由灰色理論預估期望訊號值，進而執行電腦模擬控制。本文應用灰色理論預估期望訊號之準確性已可接受；而利用此預估期望值實施電腦模擬控制之結果亦值得再以即時控制驗證之，是故本文之研究將可提供混合型噪音控制系統研發之多項參考依據。

The purpose of this study is to explore the effects of sound elimination in a cylindrical duct by combining a reactive muffler and active noise control (ANC) system. In this system, an FIR filter combined adaptive algorithm of least mean square (LMS) is adopted. The results of control for sound are compared between those before the muffler and after the muffler installed. The results indicate that the sequence of arrangement of muffler can influence the results of noise control. According to the results of experiment and simulation, the effect of noise reduction in ANC system is influenced extremely by reference signal received. The applicability and optimum position of reference signal are explored to improve the ANC system. The transmission loss and insertion loss in this system are also discussed in details. Besides, the experimental results indicate that the hybrid system has the advantages over a traditional muffler when the muffler is not designed for the frequency of the noise. Furthermore, the mathematic simulation for acoustic field in a cylindrical duct with a muffler is performed in order to verify the experiment results. In the ANC system, it seems that the order of FIR filter and step size of adaptive least mean square (LMS) algorithm will influence the result of noise control. A computer simulation for execution ANC in a cylindrical duct was performed to explore the relations between these parameters. Finally, Grey theory is applied to estimate the expected signals in order to perform a computer simulation of grey prediction to explore effects of the ANC system. The results indicate that application of Grey theory gives a good control for the hybrid system.

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