氣球幕之水下低頻噪音減噪效益精進研究

Abstract

由於氣泡在實際海洋中的穩定度不盡理想，所以將改變過去氣泡幕減噪的形式，採用氣球進行減噪實驗，透過氣泡共振現象(Bubble Acoustic Resonance Phenomena)之研究方法與加入薄膜理論的Church數學模型[1]進行減噪分析，林等人[2]指出單一尺寸減噪效益影響頻段有限，而本研究結合半徑5公分與7公分氣球的減噪頻段，利用兩種尺寸組合之氣球幕，提升100 Hz到1000 Hz頻段內的減噪效益，從探討各項參數對氣球幕減噪效益的影響，設計混和氣球幕，第一部分為氣球尺寸對減噪頻段的影響，探討適用於低頻打樁噪音的氣球尺寸，第二部分為體積分率對氣球幕減噪效益的影響，量測體積分率與減噪效益間的增益，第三部分比較混和尺寸的氣球幕與統一尺寸氣球幕間減噪的效果，與前兩部分實驗結果比對，並利用線性迴歸分析方式，於判定係數高於0.9之160 Hz到760 Hz頻段，預測體積分率對減噪效益的影響，由預測減噪效果完成參數配置，提供後續實際海域減噪工法的氣球幕設計。

Underwater noise mitigation effect is enhanced with balloon arrays for the stability and noise mitigation effects of bubble curtain in the ocean is limited. The noise mitigation effect is analyzed with bubble resonance theory incorporated into the film theory of the Church mathematical model[1]. Lin et al[2] reported the noise mitigation effects of one-size balloon curtain limited with frequency bandwidth, thus this study uses a balloons of two different radius, i.e. 5 cm and 7 cm, to form an array and its noise mitigation in respective frequency ranges. Result shows that using balloon array composed of balloons of two sizes, the noise mitigation effects are enhanced from 100 Hz to 1000 Hz. Design parameters of the balloon array is also considered while the noise mitigation effects of balloon array in various setup. The first parameter is the balloon size and its effect on the frequency of noise mitigation; The second parameter is the volume fraction and its impact on noise mitigation. The third parameters is the comparison of noise mitigation effect of balloon array composed of mixed sizes and of uniform size, with respect to the balloon size and volume fraction. Finally using linear regression analysis to predict the effect of volume fraction on noise mitigation in the frequency bandwidth of 160 Hz to 760 Hz. The study would provide follow-up design of the balloon array for underwater noise mitigation during pile driving, thus lower the noise impact on the marine environment.