臺灣博碩士論文加值系統

本論文內容主要是針對汽車鏈條傳動系統之噪音問題，利用以傅利葉轉換（Fourier Transform）為基礎之快速傅利葉轉換（Fast Fourier Transform）及短時傅利葉轉換（Short-Time Fourier Transform）兩種分析方法，分別對實驗中麥克風量測得到的穩態及暫態訊號進行時域（time domain）、頻域（frequency domain）、時頻域（time-frequency domain）三種分析，判斷出造成鏈條傳動系統產生噪音的可能原因為何？在確定噪音產生的原因後，進一步利用聲音全像（acoustical holography）量測技術配合平面近似聲源法理論對陣列麥克風訊號進行分析，繪製出整體及各個主要噪音頻率之鏈條傳動系統聲壓等高線分佈圖，確定鏈條傳動系統噪音產生的主要位置。為了克服平面近似聲源法理論在預測量測距離以內的聲壓值誤差太大的問題，因此將MUSIC演算法與平面近似聲源法理論結合使用來改善此問題。並且為了降低量測雜訊所造成的誤差影響，提高實驗分析結果的準確度，在平面近似聲源法理論的反算部分結合了Tikhonov Regularization理論與L-curve理論，選取最佳的調整參數來抑制雜訊。同時為了解決聲音全像量測實驗上量測麥克風不足的問題，在實驗中額外增加參考麥克風，並且利用控制系統中轉移函數的觀念，藉由參考麥克風來修正量測麥克風彼此間的相位關係。

In the present study,noise analysis of the chain transmission system in automobile is explored,First, Fast Fourier Transform and Short-Time Fourier Transform are two kinds of analytical methods used to carry out time domain analysis,frequency domain analysis and time-frequency domain analysis of analysis for stationary and non-stationary signals,The purpose of this study is to find out the possible reason for causing the chain transmission to produce the noise？

After confirming the reason why the noise is produced,acoustical holography is implemented by using a surface version of similar source method,The hologram given the chain transmission sound pressure contour distribution maps of overall frequency and each dominant noise frequency,Therefore,the noise source location of each individual dominant noise is extracted from the hologram。

In order to overcome the error of predicting sound pressure within a prediction distance by the plane surface version of similar source method,MUSIC method combined with the similar source method are used for improving the accuracy within the prediction distance,In order to reduce the effect of measuring error and to improve the accuracy of the analysis with plane surface version of similar source method,combined Tikhonov Regularization method and L-curve method are used in the analysis,Also,in order to solve the problem that the number of microphones is insufficient in acoustical holography experiment,a reference microphone is used in the experiment,By using transfer function between reference microphone and measuring microphone,a revised measure phase angle is obtained in the experiment。

目錄

摘要........................................................ I
英文摘要.................................................. III
致謝........................................................ V
目錄....................................................... VI
表目錄..................................................... IX
圖目錄...................................................... X
符號對照表............................................... XIII

第一章 緒論................................................1
1.1 研究動機........................................... 1
1.2 相關文獻回顧....................................... 1
1.3 研究內容........................................... 3

第二章 訊號分析理論........................................5
2.1 離散傅利葉轉換（Discrete Fourier Transform）........6
2.2 短時傅利葉轉換（Short-time Fourier Transform）......8
2.3 平面近似聲源法.................................... 11
2.4 Tikhonov Regularization理論....................... 14
2.5 L-curve理論........................................18
2.6 MUSIC演算法........................................26
2.7 相位修正理論...................................... 31

第三章 平面之近似聲源法電腦數值模擬.......................36
3.1 模擬一：三個點聲源位置落在虛擬座標上，單獨使用平面近似聲源法......................................................... 37
3.2 模擬二：一個點聲源位置沒有落在虛擬座標上，單獨使用平面近似聲源法......................................................... 41
3.3 模擬三：一個點聲源位置沒有落在虛擬座標上，使用平面近似聲源法結合MUSIC演算法......................................................44
3.4 模擬四：有雜訊下，一個點聲源位置沒有落在虛擬座標上，使用平面近似聲源法結合MUSIC演算法與Tikhonov Regularization理論................46
3.5 模擬五：利用相位修正理論修正非同步量測訊號.........50



第四章 實驗量測...........................................54
4.1 鏈條傳動系統噪音量測實驗.......................... 54
4.11 實驗環境與設備介紹................................ 54
4.12 實驗方法與步驟.................................... 55
4.13 實驗取樣率選取.................................... 56
4.14 鏈條傳動系統噪音量測實驗結果分析與討論............ 57

4.2 鏈條傳動系統全像量測實驗.......................... 64
4.21 實驗環境與設備介紹................................ 64
4.22 實驗取樣率選取.................................... 64
4.23 陣列麥克風間距設定................................ 65
4.24 實驗方法與步驟.................................... 66
4.25 鏈條傳動系統全像量測實驗結果分析與討論............ 67

第五章 結論與未來展望.................................... 72
5.1 結論.............................................. 72
5.2 未來展望.......................................... 74

參考文獻................................................... 75

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