本研究目的在於參考前人量測水下目標物散射強度與型態 (pattern) 之機構與流程，建置一套量測水下散射聲場的實驗系統。使用 Borland C++ Builder 軟體遙控台車作定點運動；以 Matlab 自動處理訊號並取得強度；規劃標準操作流程簡化實驗過程；增設監視設備確保周邊安全，有效地縮短實驗時間，改善實驗人員工作環境，使實驗過程更趨於客觀，減少人為操作之步驟，朝向量測實驗自動化發展。本系統結合中山大學海下技術研究所之大型聲學實驗水槽 (4mx3.5mx2m)，量測直徑 60 mm 銅球之散射聲場。使用具有指向性、主要發射及接收頻率響應為192k Hz 高頻之 iTP-192k 換能器為聲源及接收器。操作聲源每 3.8 Hz 間歇發射 64 個正弦波群為入射訊號，以避免邊界反射訊號干擾。控制三維運動台車及旋轉機構，改變接收器之接收方位，量測距離目標物1 m 之平面環場散射聲場。參考 Ding (JASA, 101(6), p.3398-3404, 1997) 前散射 (forward scattering) 訊號處理方法，並修正訊號處理適用之範圍，在前散射角度 0°~6° 及 354°~360° 不使用任何訊號處理濾除直達波訊號干擾。以 Hickling (JASA, 34(10), pp.1582-1592, 1962) 之彈性球體散射方程式為理論基礎，研究成果顯示前、逆散射聲場皆呈現對稱分佈，分佈型態與理論大體一致。在逆散射 (backward scattering) 區域內，誤差約在 1~2 dB。前散射因受限於直達波影響，在干擾較輕微的區域 (30°~60° 及 300°~330°)，誤差約在 2 dB 之內；其餘干擾較嚴重的區域，誤差約 -2~-9 dB。整體而言，本實驗系統之量測機構、應用程式及程序設計可信，適用於未來進行目標物散射量測實驗前之系統校正，並且應用於不同材質、外型特徵之水下目標物散射訊號分析。

The aim of this research is to establish a measurement system to acquire 2-D sound scattering field by an underwater target. In the system, A 3-DOF (degree of freedom) block is remotely orientated by Borland C++ Builder programming language and the batch-processing for signals is used to estimate strength by programing language, Matlab. The process of experiment is simplified by standard operating procedure and the safty of facilities is controled by monitor. Based on the improvements above-mentioned, we can develop an more automatical system to save time effectively, better work conditions, reduce personnel cost, and acquire more objective outcomes. We set up experiment in an water tank of dimension 4mx3.5mx2 m, located in National Sun Yat-sen University, and choose a copper sphere of diameter 60 mm as target. The projector and receiver both are iTP-192k transducer with directivity and frequency response at 192k Hz. In order to measure the 2-D scattering field at 1 m from target without strong boundary interference, projector transmits 64 sine waves at 3.8 Hz and receiver changes direction by block and rotating mechanisms. The effects of direct signal in forward scattering field can be reduced by modified signal process according to Ding (JASA, 101(6), pp.3398-3404, 1997). The difference between actual and theoretical magnitude, based on Hickling (JASA, 34(10), pp.1582-1592, 1962), is 2~3 dB in most of backward scattering region and parts of forward scattering region (30°~60° and 300°~330°), and 5~10 dB in else forward scttering range. Generally speaking, that experimental result displays symmetrical distribution corresponds with theory and indicates the design of mechanism, software and procedure in this study practicable and useful for further research in the future.

誌謝....................................................................i
中文摘要............................................................iii
英文摘要............................................................iv
第一章 緒論......................................................1
1.1 研究背景....................................................1
1.2 研究歷程....................................................3
1.3 研究動機與目標........................................3
1.4 文獻回顧....................................................6
1.5 論文範疇....................................................7
第二章 量測系統建置......................................8
2.1 設計概念....................................................8
2.2 硬體設施....................................................10
2.2.1 大型聲學實驗水槽.................................13
2.2.2 三維運動台車.........................................14
2.2.3 第四軸旋轉機構.....................................16
2.2.4 輔助裝置.................................................17
2.3 軟體設計....................................................22
2.4 實驗儀器....................................................23
第三章 量測規劃與程序..................................27
3.1 量測規劃.....................................................27
3.1.1 座標定義.................................................29
3.1.2 量測限制.................................................30
3.1.3 聲源效能分析.........................................30
3.2 量測程序.....................................................31
3.2.1 聲源設定.................................................32
3.2.2 聲源軸向調整.........................................33
3.2.3 聲速測定.................................................36
第四章 資料處理..............................................39
4.1 資料處理流程.............................................39
4.2 穩態電壓判讀.............................................41
4.3 前散射訊號處理方法.................................42
4.4 前散射訊號處理區域.................................42
第五章 系統測試：銅球散射聲場量測...........47
5.1 相關理論.....................................................47
5.1.1 型式函數..................................................47
5.1.2 散射聲壓強度公式..................................50
5.2 理論參數分析.............................................51
5.3 目標物不同懸吊方式之測試結果.............55
5.4 分析與討論.................................................59
5.4.1 對稱性分析..............................................59
5.4.2 誤差分析..................................................61
第六章 結語.......................................................66
6.1 結論.............................................................66
6.2 建議.............................................................67
6.3 未來展望.....................................................68

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