本文主要目的在於提供不同於過去主動式噪音控制之新概念並落實，在過去主動式噪音控制理論多為LMS演算法(Least Mean Square Method)搭配FIR濾波器(Finite Impulse Response)或是IIR(Infinite Impulse Response)作為控制器，其優點在於可控制寬頻噪音，但本文中所探討噪音對象則為低頻具連續性噪音，由於連續噪音具有單調性與週期性故有容易預測之特性。
　　本文中數位控制器設計主要概念為利用快速傅立葉轉換(Fast Fourier Translate, FFT) 尋找出空間噪音中最低基頻載波即第一主頻，輔以交互相關分析(Cross Correlation)分析噪音源與其下游受控噪音相位後發出另一反相位聲波，藉由抵消基頻載波擾動以收控制噪音之效果。

The goal of this study is to propose a new method of the implementation of Active Noise Control. People usually use Least Mean Square algorithm (LMS), Finite Impulse Response filter (FIR), or Infinite Impulse Response filter (IIR) as controlling means to reduce the wide band noise. In this study, it is targeting at low frequency, narrow band and continuous humming noise. The main procedures applied in the controller include using Fast Fourier Transformation to find out the dominant frequency of noise and using Cross Correlation to adjust the phase lag of the output sound signal according to the incoming one. The signal with opposite phase relative to the source of the noise is output to drive the anti-sound speaker. Waves from the speaker can then cancel out and then minimize the noise.

第一章　序章	1
第一節　研究動機	1
第二節　傳統噪音控制方法	2
第三節　主動式噪音控制緣起	4
第二章　數位控制器	9
第一節　聲波性質	9
第二節　基礎公式	11
第三節　離散傅立葉轉換(DFT)	12
第四節　交互相關分析(Cross Correlation)	13
第三章　實驗建置	14
第一節　系統建置概念	14
第二節　實驗設備	18
第三節　實驗設定	20
第四節　程式操作流程	21
第四章　實驗結果	25
實驗一	28
實驗二	29
實驗三	30
實驗四	31
第五章　未來展望	33
參考文獻	34
附錄	37
i.	小野測計 MI-1432出廠測試數據	37
ii.	PCI-1711L類比輸入卡資訊	38
iii.	PCI-1721類比輸出卡資訊	39
iv.	數位控制器人機介面	40
v.	Cross Correlation次函式	41
vi.	實驗架設照片	42
vii.	Brüel & Kjær訊號放大器	43
viii.	Brüel & Kjær前置預放大器與1/2”音頭	44
ix.	12英吋低音喇叭	45

圖目錄
圖 1人耳可聽範圍 ................................................................... 2
圖 2隔音牆與聲影區 ............................................................... 3
圖 3 Paul Lueg 1936年專利設計圖 ...................................... 5
圖 4一維聲管前饋式系統示意圖 ............................................ 8
圖 5三維空間前饋式系統示意圖 ............................................ 8
圖 6壓縮相位與稀疏相位 ....................................................... 9
圖 7相位與正弦波 ................................................................... 9
圖 8複合波 ............................................................................. 10
圖 9控制器流程圖 ................................................................. 14
圖 10兩波型不完全反相示意圖 ............................................ 15
圖 11兩波型不完全同相示意圖 ............................................ 16
圖 12兩波型接近完全反相所示意圖 .................................... 17
圖 13麥克風音頭之超心型指向性 ........................................ 19
圖 14設備架設示意圖 ........................................................... 20
圖 15控制器資料計算流程 ................................................... 22
圖 16手動AI擷取示意圖 ..................................................... 23
圖 17自動擷取模式示意圖 ................................................... 23
圖 18增益值設定示意圖 ....................................................... 24
圖 19系統未開啟前時域分布 ................................................ 27
圖 20系統未開啟前頻域分布 ................................................ 27

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