臺灣博碩士論文加值系統

本研究以2001年，亞洲海域國際聲學實驗(Asian Seas International Acoustic Experiment, ASIAEX)於南海佈放水平線陣列(Horizontal Line Array, HLA)，所收集到的淺海環境聲學資料為基礎，利用其中收錄的船舶、燈泡及爆炸聲源訊號，運用波束形成法(Beamforming)計算角度上能量分佈，以了解水平線陣列位置對水下聲源定位的影響。由過去文獻中，可知水平線陣列，在方位辨認上皆有其模糊性(Ambiguity)，但可藉由操控陣列的位置，來求得聲源確切的方位，由此可見陣列位置會影響到聲源方位的判定。本研究在訊號處理上使用有限脈衝響應濾波器，得到欲分析頻率訊號，由於本實驗的水平線陣列，本身對頻率的解析只能到50 Hz，而由濾波結果得知，燈炮聲源的訊號，並不適用於水平線陣列上波束計算，但爆炸聲源訊號，則在50 Hz下仍有訊號，因此以爆炸聲源做為計算的主要聲源。由陣列測試結果可知，主波瓣與旁波瓣的產生，與陣列的長度有關，陣列長度愈長，主波瓣的解析度愈高，旁波瓣也隨之愈多，而旁波瓣則會提升在旁波瓣角度上的波束能量，以致影響到判斷主要的聲源方向。此外水平線陣列的位置，會隨著潮汐而改變，藉由實驗中都普勒流速剖面儀的資料，可估算潮汐的流向，來間接驗證陣列趨勢的變化。本研究結果主要藉由明確聲源位置，與不同的彎曲陣列位置，求得彎曲陣列上每個麥克風，到理想直線陣列之間的垂直距離，平均後獲得陣列位置的偏移量，由位置偏移量來探討其對主波瓣寬度的影響。結果得知當偏移量於10公尺左右時，主波瓣的寬度為16°，當偏移量愈大，主波瓣寬度愈大，解析度則愈低，在聲源定位上易造成模糊性。此量化結果也與實際Wolf所計算的陣列，做比較的驗證，而其變化趨勢也與模擬之結果吻合。藉由本研究之結果當可提供未來水平線陣列在聲源定位上，若有因位置而產生陣列解析度改變的參考，進而改善陣列的設計與佈放方式。

關鍵詞：水下聲源定位、水平線陣列、波束形成法、位置偏量移、陣列解析度

The study is based on the acoustic data collected by horizontal line array (HLA) of Asian Seas International Acoustic Experiment (ASIAEX) in South China Sea of 2001. Beamforming was used to localize the sound sources during the experiment, such as explosive, to understand its correlation with position deviation from the array.
According to previous studies, the horizontal line array has ambiguity in bearing identification, which was often resolved by maneuvering array’s position, therefore it can also be concluded that the well understanding of array’s position is the key to the accurate source localization. Due to the limitation of element spacing of array used in the experiment, 50 Hz is the highest frequency can be analyzed in the study, so the recorded explosive sounds were chosen for analysis. The numerical test of array has shown the width of main lobe in beamforming is reduced by the increasing total length of the array, and the energy in the side lobes would affect the accuracy of source bearing. During the experiment, the horizontal array was found, and proved indirectly by current measurement of acoustic Dopper current profiler, to be moved by tidal currents, so the deviation from the designed deploy position can be computed. The deviation was used to quantify the resolution effect on localization by the movement of array, and when there is a 10 m deviation, the width of main lobe would increase from 8° to 16° in the studied case. The experimental results match the simulations well, so it can provide a guideline in predicting the accuracy of underwater source localization when the movement of horizontal line array is possible.
Key word: underwater source localization, horizontal line array, beamforming, position deviation, array resolution

摘要 .....................................................i
Abstract ................................................ii
目錄 ...................................................iii
圖目錄 ..................................................vi
表目錄 ..................................................x
第一章 緒論 .............................................1
1.1 研究背景 ............................................1
1.1.1 聲納定位及限制...................................2
1.1.2 定位誤差成因.....................................3
1.2 相關文獻 ............................................4
1.3 研究目的 ............................................8
1.4 論文大網 ............................................9
第二章 實驗架構 .....................................................10
2.1 實驗描述 ...........................................10
2.1.1 儀器佈放時程....................................12
2.2主要接收儀器.........................................12
2.2.1 接收陣列.....................................13
2.2.2 應答器.......................................15
2.3 實驗聲源.........................................16
2.3.1 非固定聲源........................................16
第三章 相關理論 ........................................19
3.1 波束形成法 .........................................19
3.2 取樣定理 ...........................................21
3.3 濾波處理............................................22
3.4 相關性分析..........................................24
3.5 長基線定位..........................................25
第四章 訊號處理.........................................27
4.1 聲音檔案格式 .......................................27
4.2 時頻譜 .............................................28
4.3 訊號濾波 ...........................................29
4.4 陣列的解析度及旁波瓣影響............................30
4.4.1 模擬理想陣列與旁波瓣效應........................30
4.5 水文資料處理 .......................................32
4.5.1 水層溫度 .........................................32
4.5.2 聲速剖面 .........................................34
4.6 水平方向性計算......................................35
第五章 結果分析 ........................................37
5.1 水平線陣列的變化 ...................................37
5.2 陣列與海流的變化趨勢................................39
5.3 相關性分析.......................................40
5.4 聲源定位與陣列位置的相關性.......................42
5.4.1 燈泡與爆炸聲源定位...........................42
5.4.2 船舶聲源定位.................................46
5.5 模擬陣列及量化結果..................................49
5.5.1 等效陣列長度......................................50
5.5.2 實際陣列與模擬結果之比較..........................55
第六章 結論與建議 .....................................60
6.1結論 ................................................60
6.2 建議 ...............................................61
參考文獻 ...............................................62

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