本研究宗旨在於設計一套量測水下目標物散射強度（strength）與型態(pattern)之實驗測試機構與量測流程，並且以銅球理論散射解為基準，檢證本實驗設計之可行性。本研究在大小為4m × 3.5m × 2m的實驗水槽中，以窄頻訊號投射在直徑 6 cm的銅球目標物上所產生的散射聲場為測量標的。所使用的聲源包括全向性、70 kHz 之CTG-0708換能器，及指向性、192 kHz之 iTP-192k換能器，以正弦波為波形，並分別以每串長度約為 0.143 msec（10個波） 與 0.333 msec（64個波）間歇發射。在理論方面，以R. Hickling（JASA, 34, 1962, pp.1582-1592）所發展出的解析解為依據。實驗過程中發現，比較難以量測的部分乃在於前散射 (forward scattering) 的象限，因為直達波會直接影響散射波的訊號而造成干擾，其修正方法乃參考 L. Ding（JASA, 101, 1997, pp.3398-3404）發表論文中將干擾訊號濾除方式處理，並以相位差來判斷濾除後的散射波之準確性。研究中發現，在濾除干擾訊號時，必須特別注意聲源是否同步發射，以避免散射訊號的誤差。實驗結果與理論值比較後發現，在前散射部分誤差約為 3∼4 dB，而逆向散射 (backscattering) 部分誤差約 1∼2 dB，惟曲線變化形式大體一致。此一結果顯示，本實驗設計基本上可行，若再經進一步改良之後，應可作為水下目標物測量之用。整體而言，本論文分為基本理論推導、實驗儀器架設、基本的聲學量測、機構設計及實驗數據分析等部分，重點為散射實驗之設計與觀察、資料誤差分析、檢討與改進等。

The research aims to design an experimental testing mechanism and process for measuring the scattering strength and the pattern induced by an underwater target. The experimental data are to compare with existing theoretical results to insure the integrity of experimental design. The experiment is conducted in a water tank of dimension 4m x 3.5 m x 2m. The main work is to measure the sound field scattered by a copper sphere of diameter 60mm. There are two types of sources employed in this analysis: one is omni-directional, 70kHz CTG-0708 transducer, and the other is directive, 192 kHz iTP-192k transducer. Both transducers transmit sine waves with the pulse lengths roughly equal to 0.143 msec (equivalent to 10 waves) and 0.333 msec (equivalent to 64 waves), respectively. The scattering field theory is based on the formulation developed by Hickling (JASA, 34, 1962, pp.1582-1592). The experimental process has demonstrated that it is more difficult to measure the forward scattering field than the backward scattering field, due to the fact that the forward scattering field is likely to be mingled with the direct waves. To deal with this problem, the treatment developed by L. Ding（JASA, 101,1997, pp.3398-3404）has been invoked, in that the direct waves may be filtered by phase shift. This procedure requires the special concern on synchronism of sound source in order to avoid the variation of scattering signals. The comparison between experimental and theoretical results shows that the discrepancy in the forward scattering sector is within 3 to 4 dB, while in the backscattering sector, it is within 1 to 2 dB; however, generally speaking, the variation of the curves show a good agreement. These results indicate that the design of this experiment is basically practicable, and with further improvements, it could be applied to measure other underwater targets. As a whole, the thesis is composed by basic theory deduction, experimental instrumentation, mechanism design, and experiment data analysis. The emphases place on the design and observation of the scattering experiment, data analysis, and further improvement.

第一章：緒論 1
第二章：實驗理論與公式推導 5
第三章：實驗儀器與實驗方法 18
第四章：基本聲學測定與儀器效能分析 26
第五章：實驗量測結果與資料分析 37
第六章：結語和建議與未來展望 60

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