氣泡在天然的海洋中隨處可見，且含氣泡的混合液體會對聲音的傳播產生重大的影響，尤其對水下目標物的偵測造成嚴重干擾，因此，研究氣泡對聲波傳播所造成的影響，乃是一個重要研究主題。本研究利用由英國(iTP)公司所研發的聲納訓練系統(AST-Sonar System)，經由適當的外加設計，探討聲波通過氣泡幕衰減的特性。本研究首先藉由文獻回顧，彙整並推導所需公式，再藉由實驗設計，測量聲波經過氣泡幕之衰減。實驗過程則是利用鐵片所組成的平行版進行體積分率測量，並與麥克風所量的聲壓做相關分析，透過曲線的擬合表示兩者關係式。最後再將聲壓與推導的衰減係數公式比較。理論部份以質量守恆與動量守恆方式導出氣泡混合液中的聲波方程式，再配合壓力連續與壓力梯度連續的邊界條件，最後可獲得氣泡液中聲壓值解與反射聲壓值解，並進一步求得聲波之衰減係數、反射係數與透射係數。實驗則包含兩個部份，第一部份是量測氣泡幕內混合液體的體積分率，第二部份則是量測聲波通過氣泡幕的衰減。實驗結果顯示，氣泡體積分率在1％時，氣泡幕平均每公分可衰減聲波8dB左右，而高體積分率時衰減係數變大且與理論值有所差異，這是因為未加入氣泡交互作用的因素。另外，較低頻聲波會比較接近理論值而高頻聲波與理論值差異甚大，這是因為高頻聲波的波長較小，較不符合在推導過程時聲波波長必需遠大於氣泡粒徑的條件。實驗上，建議使用更恰當的換能器與更精密的氣泡石管，才能讓實驗結果更完善。

Bubbles are often present in the natural ocean. Bubbly liquid will have the significant influence the sound propagation, and creates a significant disturbance to under water target's detection. Therefore, it is an important research subject of bubble influence to the sound wave propagation. This study used the sonar training system which developed by British's iTP corporation, through suitable additional design discuss the attenuation of sound propagating through a bubble screen. At first this study collects and infers the formula by the literature review. Secondly, the experimental design of measuring the attenuation of sound wave. The experiment process by using two parallel iron boards to carry on the measurement of gas-volume fraction. Then correlate with the sound pressure from the measurement of hydrophone. After curve fitting, we can clearly know the each other correlation. Finally taking the result compare with the attenuation coefficient formula. The experimental consists of two parts. The first part is to measure the gas-volume fraction of the bubbly liquid contained in the screen; while the second part is to measure the sound attenuation of the bubble screen. The result display that the bubble screen can attenuate about 8 dB per centimeter as the gas-volume fraction stay at 1 percent. At high gas-volume fraction the coefficient of attenuation has increased, and is different from theoretical value. This is because the bubble's correlation has not been considered. In addition, the low frequency sound wave is close to theoretical value, but the high frequency sound wave has big different to theoretical value. Because the high frequency sound wave's wavelength is too small to satisfy the condition. At experiment I suggest to use more appropriate transducers and precise bubble's tube. Thus the experimental result will be better.

第一章 緒論................................................................ 1
1.1 前言...................................................................... 1
1.2 文獻回顧.............................................................. 2
1.3 研究動機與目的.................................................. 4
1.4 論文範疇.............................................................. 5
第二章 理論分析........................................................ 7
2.1 連續方程式.......................................................... 7
2.2 動量方程式.......................................................... 8
2.3 氣泡運動方程式 ................................................. 9
2.4 聲波衰減.............................................................. 10
2.5 穿透係數與反射係數.......................................... 10
第三章 實驗建置與方法............................................ 12
3.1 AST-Sonar系統介紹........................................... 12
3.2 AST 實驗應用...................................................... 19
3.3 實驗過程與感應極板製作原理.......................... 24
第四章 實驗過程與結果之討論................................ 29
4.1 空氣流量與氣泡尺寸及感應電壓之分析.......... 29
4.2 氣體流量與量測聲壓之分析.............................. 33
4.3 衰減分析.............................................................. 35
第五章 結論與建議.................................................... 41
5.1 結論...................................................................... 41
5.2 建議...................................................................... 42

附錄A 理論分析與推導............................................. 47

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