在淺海環境中，聲波受海床的影響甚鉅，故瞭解海床之地聲參數（Geoacoustic Parameters），可以提升聲納系統的使用效能。因此，本研究利用西元2001年亞洲海域國際聲學實驗(Asian Seas International Acoustic Experiment, ASIAEX)在南中國海佈放垂直線陣列(Vertical Line Array, VLA)所收錄到的船舶噪音做為聲源來反算海床的性質。首先，透過波束形成(Beamforming)計算出船舶距垂直線陣列最近的水平距離，用來設定聲學模式中點聲源的位置。在反算的過程中，假設海床的結構為兩層，故所要求得的參數分別為沈積層聲速(c1)、密度(ρ1)；底層聲速(c2)、密度(ρ2)與吸收係數(α)。在此，利用匹配聲場處理法做為反算技術的基本原理，它可視為是組合最佳化問題(Combinatorial Optimization Problem，COP)，則必須建立一個適當的成本函數。此成本函數是量化實測聲場與模式聲場之間的差異，當成本函數達到最小值時，模式化環境中所使用的預設參數，即為反算的結果，計算後所獲得的參數分別為c1＝1600 m/s、c2＝1650 m/s、ρ1=1.6 g/cm3、ρ2=2.1 g/cm3、α=0.6 dB/λ。最後，這實驗中使用掃頻聲納（Chirp sonar）在此地點之勘測結果和利用其他聲源來做反算的研究應證本研究之反算結果。

Sound propagation can be greatly affected by seabed, especially in shallow water, therefore by understanding the geoacoustic parameters of sea bottom can help to improve the performance of sonar systems. In this study, ship noise collected by the vertical line array (VLA) in South China Sea experiment of the Asian Seas International Acoustics Experiment (ASIAEX SCS) in 2001 was used as a sound source to invert the geoacoustic parameters. The nearest horizontal distance between VLA and the passing ship was estimated by beamforming the receiving sounds on the array, and this distance was used in the sound propagation modal. In the modal, two layers structure were assumed for the bottom, so the sound speed (C1) and density (ρ1) of sediment layer, sound speed (C2 ) and density (ρ2) of subbottom layer, and total absorption coefficient (α) need to be inverted. Matched field processing is used to solve this inverse problem, and computing the minimum cost function between the measured and modeled sound field, the best matched bottom parameters are C1＝1600 m/s、C2＝1650 m/s、ρ1=1.6 g/cm3、ρ2=2.1 g/cm3、α=0.6 dB/λ. These results were compared with chirp sonar survey in this area, and the agreement is satisfactory.

摘要 .................................................................................................... i
Abstract ............................................................................................... ii
目錄 .................................................................................................... iii
圖目錄 ................................................................................................ vii
表目錄 ................................................................................................ x
第一章 緒論 ...................................................................................... 1
1.1 研究動機 ............................................................................... 1
1.2 底質採樣 ............................................................................... 2
1.2.1箱型岩心採樣器 ............................................................. 2
1.2.2重力岩心採樣器 ............................................................. 2
1.2.3活塞岩心採樣器 ............................................................. 4
1.2.4震動岩心採樣器 ............................................................. 5
1.3 地聲反算 ............................................................................... 6
1.3.1震測法 ............................................................................. 6
1.3.2海底地層剖面儀 ............................................................. 6
1.3.3其他聲源之地聲反算....................................................... 8
1.4 研究目的 ............................................................................... 11
1.5 論文大網 ............................................................................... 12
第二章 實驗架構 .............................................................…………. 13
2.1 實驗描述 ............................................................................... 13
2.2 儀器佈放時程 ....................................................................... 15
2.3 主要聲學儀器 ....................................................................... 15
2.3.1 接收陣列 ........................................................................ 16
2.3.2 深海聲源 ................................….................................... 18
2.3.3 淺海聲源 ................................….................................... 20
2.3.4 拖曳式J-15-3 聲源 ................................…................... 21
2.3.5 燈泡聲源 …................................…................................ 22
2.3.6 應答器 …................................….................................... 22
2.4 水文環境 ............................................................................... 23
第三章 相關理論 .............................................................................. 25
3.1 波束形成法 ........................................................................... 25
3.2 長基線聲學方式 ................................................................... 27
3.3 取樣定理 ............................................................................... 28
3.4 訊號濾波 ............................................................................... 29
3.5 相關性分析 ........................................................................... 31
3.6 反射係數 ............................................................................... 32
3.7 匹配聲場 ............................................................................... 33
3.7.1 聲學模式 ........................................................................ 33
3.7.2 匹配聲場處理法的成本函數 ........................................ 34
3.7.3 靈敏度分析與誤差估計 ................................................ 34
第四章 訊號處理 .............................................................................. 36
4.1 聲音檔案格式 ....................................................................... 36
4.2 三維頻譜 ............................................................................... 37
4.3 訊號濾波 ..........…................................................................. 37
4.4 陣列有效計算角度與校正 ................................................... 39
4.5 波束能量的計算過程 ........................................................... 41
4.6 水文資料處理 ....................................................................... 42
4.6.1 水壓資料 ........................................................................ 42
4.6.2 聲速剖面 ........................................................................ 43
第五章 結果分析 .............................................................................. 45
5.1 聲源定位 ............................................................................... 45
5.2 海床損失與反射係數 ........................................................... 48
5.3 聲場模擬 ............................................................................... 52
5.4 靈敏度分析 ....................................................................... 54
5.5 參數反算結果 ....................................................................... 57
第六章 結論與建議 ........................................................................ 62
6.1結論 ........................................................................................ 62
6.2 建議 ....................................................................................... 63
參考文獻 ............................................................................................ 64
附錄...................................................................................................... 66

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