- 學位論文
結合被動式與主動式噪音控制於通風管
Integration of passive and active noise control techniques for ventilation ducts
摘要
本論文以數位訊號處理器(Digital Signal Processor, DSP)實現主動噪音控制(Active Noise Control, ANC)，實際使用不同形狀的真實通風管。 在許多場所可見通風管的存在，而通風管主要用於將工廠裡的廢氣或油煙透過管路設備排出，但是這些設備於管口產生噪音，使工廠人員或是附近住戶深受其擾。過去管道中的噪音會透過被動噪音控制(Passive Noise Control, PNC)的技術將噪音在管道中做消除，不過考慮到油煙在管內形成的汙垢，這對於被動噪音裝置會造成不小的負擔可能需要清洗與更換，另外一個原因是被動噪音控制無法有效地將低頻消除，因此我們結合被動噪音控制和主動噪音控制的技術，能夠成功將通風管內的聲音消除。 本實驗將會實際應用在不同形狀的通風管上，將圓管和方管的噪音透過被動噪音控制的技術結合主動噪音控制在管口位置達成噪音消除，並分析被動噪音控制將高頻衰減和結合主動噪音控制在小於截止頻率的頻寬作降噪，是比起單純使用主動噪音控制的效果還要好，最後提出了對於通風管的三種改善，以穩定實際應用在不同場域下通風管的噪音。
並列摘要
This thesis uses the digital signal processor (DSP) to implement active noise control (ANC) techniques for ventilation duct. The ventilation duct is mainly used to discharge the exhaust gas or lampblack in the factory. But it generates noise at the open end of the duct, which annoys the factory workers and nearby residents a lot. We reduce noise at the position of the open end of the duct using active noise control. Since the noise in the ventilation duct includes wind noise and unstable airflow, if the microphone is directly facing wind, it will lead to deficient performance. In this paper, active noise control is combined with passive scheme to reduce duct noise at high frequency. An effective way to avoid deficient performance of microphone due to strong wind is also suggested. Several experiments are practically fulfilled using real ventilation ducts with different shapes, and the noise will be eliminated through passive noise control technology combined with active noise control at the end of the duct. Integration of passive and active noise control techniques for ventilation duct to reduce noise is better than only using active noise control. Finally, three improvements to the ventilation duct are proposed to stabilize the actual application of the ventilation duct in different places.