聲波作為水下傳輸訊息唯一的有效方式，水下通訊乃是水聲應用的重要研究主題。由於受到多重傳播路徑的影響，水下通訊向來是一個複雜的問題，尤其是在水聲分佈不均勻的淺海環境中，此一問題更為嚴重。過去有關水下通訊的研究，大多以數值模擬或實驗室實驗為主，而較少在實海域進行。緣此，臺灣大學海洋研究所、美國海軍研究實驗室（Naval Research Laboratory, NRL）、中山大學水中聲學研究室等研究團隊，乃於2011年5月，在高雄西子灣海洋實驗場，進行一項為期一週的實海域水下網絡、水下通訊及水聲層析實驗（Underwater Networking, Communication, and Acoustic Tomography）。本研究乃利用該實驗所獲得之局部資料，進行水聲層析應用於淺海流場估算之可行性評估。實驗以9組水下數據機分佈於範圍約三十平方公里為架構，發射訊號採用M序列來進行相位調變，並使用高精準度的GPS計時器來作時間同步，同時收集海洋水文、環境及動態資料。藉由測站間訊號來回發射與接收，精確量測聲波的傳播時間，探討高頻聲波於淺海環境中，因受流場變化的影響所造成來回傳遞走時差的變化，藉此估算沿著聲線上的平均流速，並與交通部港灣技術研究中心的氣象浮標所提供的海流資料做比對。結果顯示雖有部份資料顯示流向不符，但其估算出來的流速大小仍屬合理範圍。觀察其大部分時間都落在沿著聲線上的流向改變前或低流速時，其可能原因為西子灣海洋實驗場是以地形流為主，所以當流向改變時，其流場變化會較複雜。但由大部分資料顯示是具體可行的，這也驗證了水聲層析應用於淺海流場估算之可行性。最後，本研究使用一種不需複雜數學運算來估算二維流場的方法，並藉由蒙地卡羅方法探討測站間的夾角對估算流速誤差之影響。

Underwater communication is an important research of applied underwater acoustic since sound wave is the only effective way of transmitting messages under water. Underwater communication has always been a complicated problem especially in the shallow water environment due to the influence of multipath propagation. In the past, research on underwater communication had been done mostly by numerical simulation or laboratory experiments instead of doing in real oceanic areas. As a result, several research teams such as the Institute of Oceanography in Taiwan University, the Naval Research Laboratory and the acoustic laboratory of National Sun Yat-sen University Institute of Applied Marine Physics and Undersea Technology had executed a one-week real oceanic area experiment of underwater networking, communication, and acoustical tomography in Sizih Bay Marine Test Field. The experiment adopted 9 sets of underwater modem distributed within the range of 30 square kilometer to transmit, receive signals and collect CTD data. This research adopted part of the data gained from the experiment mentioned above to progress the feasibility test of acoustic tomography on current estimate to shallow water environment. By transmitting and receiving signals between stations, This research study the travel time difference between transmitting signals forward and backward caused by the flow field when using high frequency source in shallow water environment. This research estimated the average current speed and compared it to the weather buoy data from the Harbor and Marine Technology Center. This research discovered that most of the estimated results correspond to the weather buoy's ADCP data. Finally, this research adopted the method which does not require complex mathematics operation to estimate the two-dimensional flow field, and probe into what influence the angle between stations would bring to the deviation of estimating flow speed by using the Monte Carlo method.

第一章 緒論 1
1.1 研究主題與研究動機 1
1.2 文獻回顧 2
1.3 西子灣海洋實驗場相關實驗之回顧 3
1.3.1 環境調查分析 3
1.3.2 高雄第一港區水下噪音特性研究 5
1.3.3 水聲傳播實驗 6
1.3.4 港區內水下反入侵偵測實驗 7
1.3.5 地聲反算實驗 9
1.3.6 混響性質之研究 12
1.3.7 水下網絡通訊及水聲層析 14
1.4 研究方法 14
1.5 論文範疇 15
第二章 相關理論 16
2.1 水聲層析原理 16
2.1.1 前言 16
2.1.2 水聲層析技術 17
2.1.3 平均聲速及流速 19
2.2 淺海環境中聲波傳播模式 20
2.2.1 基礎聲線理論 20
2.2.2 多重路徑效應 22
2.3 短時距傅立葉轉換 23
2.4 奈奎斯特取樣原理 24
2.5 脈衝壓縮技術 27
2.5.1 調變 28
2.5.2 最大長度序列 29
2.5.3 發射訊號模擬 30
第三章 水聲層析實驗 32
3.1 實驗場址與環境資訊 32
3.2 實驗儀器 35
3.2.1 水下數據機 35
3.2.2 無線電接收盒 36
3.3 實驗流程 38
3.4 訊號處理 39
3.5 資料篩選 42
3.5.1 訊雜比 42
3.5.2 訊號走時與時間補償 44
3.5.3 資料分類與統計 46
3.6 訊號來回傳遞走時估算 51
3.7 二維流場分布圖 53
第四章 實驗結果與討論 58
4.1 發射訊號驗證 58
4.2 氣象浮標資料 58
4.3 水聲層析估算流速與氣象浮標資料比較 61
4.4 水聲層析估算流場 63
第五章 結論與建議 76
5.1 結論 76
5.2 檢討與建議 77
參考文獻 78
附錄A 水聲層析應用於淺海流場估算之可行性評估 81
附錄B 出海日誌 91

[1] Baggeroer, A., Munk, W. (1992). The Heard Island Feasibility Test, Physics Today.
[2] Behringer, D., Birdsall, T., Brown, M., Cornuelle, B., Heinmiller, R., Knox, R., Metzger, K., Munk, W., Spiesberger, J., Spindel, R., Webb, D., Worcester, P., Wunsch, C. (1981). A demonstration of ocean acoustic tomography, Nature. Vol.299, pp. 121-125.
[3] Kaneko, A., Yamaguchi, K., Yamamoto, T., Gohda, N., Zheng, H., Syamsudin, F., Lin, j., Nguyen, H. Q., Matsuyama, M., Hachiya, H., Hashimoto, N. (2005). A coastal acoustic tomography experiment in the Tokyo Bay, Acta Oceanologica Sinica, Vol. 24, No. 1, pp. 86-94.
[4] Lin, j., Kaneko, A., Yamaguchi, K., Gohda, N. (2005). Accurate imaging and prediction of Kanmon Strait tidal current structures by the coastal acoustic tomography data, Geophys. Res. Lett, Vol. 32, L14607, pp. 86-94.
[5] Munk W, Worceser P F, Wunsch C. (1995). Ocean Acoustic Tomography, Cambridge: Cambridge UP, pp. 1-433.
[6] Munk, W., Wunsch, C. (1979). Ocean acoustic tomography: a scheme for large scale monitoring, Deep-Sea Research. Vol.26A, pp. 123-161.
[7] Taniguchi, N., Huang, C. F., Kaneko, A., Liu, C. T., Wang, Y. H., Yang, Y., Howe, B. M., Lin, J., Zhu, X., Gohda, N. (2012). Measuring the Kuroshio current with ocean acoustic tomography (submitted to J. Acoust. Soc. Am.).
[8] Nguyen, H. Q., Yamoaka, H., Kaneko, A., Lin, j., Yamaguchi, K., Gohda, N., Takasugi, Y. (2009). Acoustic measurement of multisubtidal internal modes generated in Hiroshima Bay, Japan, IEEE J. Oceanic Eng, Vol. 34, No. 2, pp. 103-112.
[9] Park, J. H., Kaneko, A. (2000). Assimilation of coastal acoustic tomography data into a barotropic ocean model, Geophys. Res. Lett, Vol. 27, No. 20, pp 3373-3376.
[10] Senda, U., Worcester, P. F., Cornuelle, B. D., Tiemann, C. O., Baschek, B. (2002). Integralmeasurements of masstransport and heat content in the Strait of Gibraltar from acoustic transmissions, Deep-Sea Research Part II, Vol. 49, pp. 4069-4095.
[11] Stoughton, R. B., Flatte, S. M., Howe, B. M. (1986). Acoustic measurments internal wave rms displacement and rms horizontal current off Bermuda in late 1983, Geophys. Res. Lett, Vol.26, No.C6, pp. 7721-7732.
[12] Urick, R. J. (1983). It Principles of Underwater Sound (3rd ed.). Washington DC: McGraw-Hill.
[13] Yamaguchi, K., Lin, j., Kaneko, A., Yamamoto, T., Gohda, N., Nguyen, H. Q., Zheng, H. (2005). A continuous mapping of tidal current structures in the Kanmon Strait, J. Oceanogr, Vol. 61, pp. 283-294.
[14] Yamoaka, H., Kaneko, A., Park, J. H., Zheng, H., Gohda, N., Takano, T., Zhu, X. H., Takasugi, Y. (2002). Coastal acoustic tomography system and its field application, IEEE J. Oceanic Eng, Vol. 27, No. 2, pp. 283-295.
[15] Yang, T. C., Schindall, J., Huang, C. F., Liu, J. Y. (2010). Underwater-intruder detection in harbor environments using Doppler-sensitive waveforms (submitted to IEEE J. Oceanic Eng.).
[16] Yuan, G., Nakano, I., Fujimori, H., Nakamura, T., Kamoshida, T., Kaya, A. (1999). Tomographic measurements of the Kuroshio Extension meander and its associated eddies, Geophys. Res. Lett, Vol.26, No.1, pp. 79-82.
[17] Zheng, H., Gohda, N., Noguchi, H., Ito, T., Yamaoka, H., Tamura, T., Takasugi, Y., Kaneko, A. (1997). Reciprocal sound transmission experiment for current measurement in the Seto Inland Sea, Japan, J. Oceanogr. Vol. 53, pp. 117-127.
[18] 林祐德 (2011)，「西子灣海洋實驗場混響性質之研究」，國立中山大學海下科技暨應用海洋物理研究所碩士論文。
[19] 張舜傑 (2010)，「西子灣海洋實驗場水聲傳播及地聲反算之研究」，國立中山大學海下科技暨應用海洋物理研究所碩士論文。
[20] 許登壹 (2007)，「西子灣海洋實驗場環境調查分析之研究」，國立中山大學海下技術所碩士論文。
[21] 郭晉麟 (2010)，「都卜勒頻譜於港區環境中水下目標物偵測之應用」，國立中山大學海下科技暨應用海洋物理研究所碩士論文。
[22] 陳常侃，王鵬華，丁建均(2011)，『離散時間訊號處理(第三版)』，全華圖書。
[23] 趙尊憲 (2007)，「高雄港第一港口水下噪音特性之研究」，國立中山大學海下技術研究所碩士論文。
[24] 劉金源 (2001)，『水中聲學-水聲系統之基本操作原理』，國立編譯館。
[25] 劉金源 (2001)，『海洋聲學導論-海洋聲波傳播與粗糙面散射之基本原理』，中山大學出版社。
[26] 蕭明亨 (2009)，「西子灣極淺海域水聲傳播實驗」，國立中山大學海下科技暨應用海洋物理研究所碩士論文。