臺灣博碩士論文加值系統

本研究為了解南海海域沙波地形特性，以及此地形對聲波傳遞的影響，與台大及美國NPS合作在2012年5月於南海進行實海域的沙波探測實驗，以多音束回聲聲納系統進行大範圍的海底沙波地形掃測，除了蒐集環境資料外，也以此環境測量結果來進行2013年5月的沙波聲學實驗的規劃，此實驗中以較密集的測線進行多音束回聲聲納系統的掃測，獲得了更精細的沙波地形探測結果，並經由兩年度的沙波探測結果比對，觀察到此處沙波地形的特性，而2013年的聲學實驗中，則是以聲學記錄錨碇為圓心，拖曳一半徑5km的圓，藉此得到不同方位下，沙波地形對聲波傳遞所造成的能量變化，並藉由BELLHOP與RAM-PE兩種數值模式，來探討沙波地形的存在與否，對多路徑效應與通道訊號能量結構所產生的影響。由沙波探測的結果可以發現，南海地區的沙波走向多與等深線同為東北-西南走向，其分佈無特定規則，地形時而平坦時而有沙波存在，此處大陸斜坡上之沙波波高多在10m內，僅觀察到少部分約20m高的沙波地形，且由兩年度的沙波地形變化相互比對可發現其沙波變動量小。而由聲學實驗的實測資料與數值模擬之結果，得到沙波地形的存在會影響通道多路徑效應，也會造成聲波能量在水表層的大量衰減現象，且當聲線與沙波走向垂直時，可以看到明顯的能量衰減，此外，若不考慮沙波地形，當地勢由爬坡地形轉為降坡地形時，則通道訊號能量會往水表處集中。
本研究之成果可做為日後在沙波地形的海域下進行音傳實驗時的參考資料，並可進一步運用於討論海底沙波地形對聲波通訊所造成之影響。

To study the characteristics of sand dunes in the South China Sea (SCS) and its effects on sound propagation, the pilot experiment of the Acoustic Sand Dune Experiment was carried on in May 2012, used a multi-beam echo sounder collecting the topographic data. The intensive observation phase of the Sand Dune Acoustic Experiment in May 2013 is planed based on the resluts of the pilot experiment, which achieve finer measurement: multi-beam echo sounder. The characteristics of sand dunes can be obtained by comparing the results of 2012 and 2013. Furthermore, the acoustic experiment was conducted in 2013; the acoustic recorders were deployed at the center and the source was towed with a 5 km radius circle to obtain the energy fluctuation under different sand dunes structure. This data was used to discuss the impact on multipath effect and energy distribution caused by sand dunes. Moreover, two numerical models: BELLHOP and RAM-PE were applied to model the propagation effects in sand dune field. The results shows that sand dunes on the upper continental slope in SCS were extended in the northeast-southwest direction; and most of its amplitude are less than 10 m, only few were observed over 20 m. From the survey results of this two years, we can see the amount of variation was small and from experiment data and numerical modeling, we can see that the sand dunes will have significant impact on multipath effect, ans also cause a great loss near sea surface. In addition, without considering the sand dunes, when the terrain change from upslope to downslope, signal energy will concentrate on the surface layer of water. This research can be used as a reference for future experiments, and be further applied to discuss the acoustic communication performance caused by the sand dunes.

目錄
論文審定書 i
誌謝 ii
中文摘要 iii
英文摘要 iv
目錄 v
圖次 vii
表次 ix
第一章 緒論 1
1.1 研究背景及動機 1
1.2 文獻回顧 2
1.3 研究目的與方法 4
1.4 論文架構 5
第二章 沙波探測及聲學實驗簡介 7
2.1 2012沙波地形探測實驗簡介 9
2.2 2013沙波地形探測實驗簡介 12
2.3 音傳實驗簡介 16
2.3.1 拖曳式聲納系統 19
2.3.2 聲學記錄錨碇串 23
2.4 海洋物理環境概況 27
第三章 訊號處理與數值方法 31
3.1 脈衝壓縮 32
3.2 均方根壓與聲壓位準 35
3.3 移動平均濾波 37
3.4 聲學模組計算理論 38
3.4.1 數值模式BELLHOP計算理論 39
3.4.2 數值模式RAM計算理論 41
第四章 音傳資料分析與數值模擬 43
4.1 脈衝響應與數值模擬分析 44
4.1.1 實測資料分析 45
4.1.2 數值模擬分析 47
4.2 聲壓位準與音傳損耗模擬 50
4.2.1 方位角300-A度與方位角300-B度的聲壓位準比較 51
4.2.2 方位角120度下，沙波地形與平坦地形的模擬比較 56
4.2.3 方位角300度下，沙波地形與平坦地形的模擬比較 58
4.2.4 方位角120度的與方位角300-B度的聲壓位準衰減討論 60
第五章 結論 62
參考文獻 64

[1] Reeder, D. B., Ma, B. B., and Yang, Y. J. (2011) “Very large subaqueous sand dunes on the upper continental slope in the South China Sea generated by episodic, shoaling deep-water internal solitary waves” Mar. Geol., Vol. 279, pp. 12–18.
[2] Ashley, G.M., (1990) “Classification of large-scale subaqueous bedforms: a new look at an old problem.” Journal of Sedimentary Petrology,. Vol. 60, pp. 160–172.
[3] Heezen, B.C., Hollister, C.D., (1971) The Face of the Deep. Oxford University Press, New York, NY.
[4] Wynn, R.B., Stow, D.A.V., (2002) “Classification and characterization of deep-water sediment waves.” Marine Geology., Vol. 192, pp. 7–22.
[5] Cai, A., Zhu, X., Li, Y., Cai, Y., (2003) “Sedimentary environment in the Taiwan Shoal.” Marine Georesources and Geotechnology., Vol. 21, pp. 201–211.
[6] Ediger, V., Velegrakis, A.F., Evans, G., (2002) “Upper slope sediment waves in the Cilician Basin, northeastern Mediterranean.” Marine Geology., Vol. 192, pp. 321–333.
[7] Jordan, G.F., (1962) “Large submarine sand waves.” Science., Vol. 136, pp. 839–848.
[8] Ching-Sang Chiu, Steven R. Ramp, Christopher. W. Miller, James. F. Lynch, Timothy. F. Duda, and Tswen Yung Tang., (2004) “Acoustic intensity fluctuations induced by South China Sea internal tides and solitons.” IEEE J. Oceanic Eng., Vol. 29, pp. 1249-1263
[9] 胡文正，”水下水平陣列位置不確定性對聲源定位的影響”，國立中山大學海下技術研究所碩士論文，2006。
[10] 林穎聰，” ASIAEX南海實驗中爆炸聲源之聲學反算”，國立台灣大學工程科學及海洋工程研究所博士論文，2004。
[11] Chiu, Y. S. (2013)” Enhanced acoustic mode coupling resulting from an internal solitary wave approaching the shelfbreak in the South China.” J.Acoust. Soc. Am., Vol. 133, pp. 1306-1319.
[12] 廖柏智，”孤立內波與沙波形成之數值模擬研究”，國立中山大學海下科技技應用海洋物理研究所碩士論文，2011。
[13] Chiu, Y. S. and Reeder D. B. (2013) “Acoustic mode coupling due to subaqueous sand dunes in the South China Sea” J. Acoust. Soc. Am., Vol. 134, pp. 198-204.
[14] Chang, Andrea Y. (2014) ”Three-dimensional acoustic propagation effect in subaqueous sand dune field” J. Acoust. Soc. Am., Vol. 136, pp. 2178-2179.
[15] 劉孟竺，” 三維海洋音傳與海床沙丘效應之研究”，國立台灣大學工程科學及海洋工程學研究所碩士論文，2014。
[16] Collins, M. D. (1988) FEPE User’s Guide, NORDA Technical Note 365 (Naval Research Laboratory, Stennis Space Center, MI).
[17] Shang, E. C. and Wang, Y. Y. (1993) “Acoustic travel time computation based on PE solution” J. Comp. Acoust., Vol. 1, pp. 91-100.
[18] Mackenzie, K. V., (1981) “Nine-term Equation for Sound Speed in the Oceans,” J. Acoust. Soc. Am., Vol. 70, pp.807.
[19] Wentworth, C. K. (1922) &;quot;A scale of grade and class terms for clastic sediments&;quot; J. Geology., Vol. 30, pp. 377-392.
[20] Harrison, C. H. and Harrison, J. A. (1995) “A simple relationship between frequency and range averages for broadband sonar” J. Acoust. Soc. Am., Vol. 97, pp. 1314–1317.
[21] DiNapoli, F. R. and Deavenport, R. L. (1980) ”Theoretical and numerical Green’s function field solution in a plane multilayered medium” J. Acoust. Soc. Am., Vol. 67, pp. 92–105.
[22] Pierce, A. D. (1965) “Extension of the method of normal modes to sound propagation in an almost-stratified medium” J. Acoust. Soc. Am., Vol. 37, pp. 19-27.
[23] Porter, M. B. and Bucker, H. P. (1987) ”Gaussian beam tracing for computing ocean acoustic fields” J. Acoust. Soc. Am., Vol. 82, pp. 1349-1359.
[24] Alterman, Z. and Karal, F. C. (1968) ” Propagation of elastic waves in layered media by finite-difference methods” Bull. Seis. Soc. Am., Vol. 58, pp. 367-398.
[25] Hard, R. H. and Tappert, F. D. (1973) ”Applications of split-step Fourier method to the numerical solution of nonlinear and variable coefficient wave equation” SIAM Rev., Vol. 15, pp. 423.
[26] Porter, M. B. and Bucker, H. P. (1987) ”Gaussian beam tracing for computing ocean acoustic fields” J. Acoust. Soc. Am., Vol. 82, pp. 1349-1359.
[27] Collins, M. D. (1993) ”A split-step pade solution for the parabolic equation method” J. Acoust. Soc. Am., Vol. 93, pp. 1736-1742.