水下超穎聲學二極體結構之吸音機制探討與充水阻抗管實驗驗證

Abstract

本研究以空腔吸音結構為基礎，考慮不同材料組合對吸音係數的影響，此吸音材結合了斜面、雙橡膠、空腔的概念實現具有單向傳輸性能的水下超穎聲學二極體結構，為水下超穎材料提出一種新的設計方向。本研究所使用之吸音材先由簡易均質的純材料結構進行嘗試製作，並以實際的材料參數以及有限元素模擬進行輔助建構阻抗管尺度的試片驗證實驗及模擬結果是吻合的。透過有限元素模擬進行模型優化後決定以丁腈橡膠及三元乙丙橡膠組合進行二極體結構試體製作與吸音係數量測。將製作出的最佳化試片使用本實驗室建置的充水阻抗管進行三參數校正法的實驗量測，實驗量測結果顯示在3000到10000 Hz之內皆達到正向入射吸音係數有達0.6以上，而反向入射吸音係數皆在0.2以下，且由正反向入射有明顯的單向傳輸結果，而有限元素模擬也獲得相同的趨勢。最終透過實驗與有限元素模擬證明模型具有二極體效果，說明本研究所提出的結構設計有實際上應用之潛力。

This study based on cavity sound-absorbing structure, consider effect of different material combinations for sound absorption coefficient. The structure uses idea of bevel, double rubber, and cavity to realize an underwater acoustic diode metamaterial structure with unidirectional transmission performance. Propose a new design direction for underwater sound-absorbing materials. The sound-absorbing materials used in this study are firstly made from homogeneous material structure, and use actual material parameters and finite element simulation to construct test sample of impedance tube scale to verify that the experimental and simulation results are consistent. After optimizing model through finite element simulation, we selected combination of NBR and EPDM rubber for diode structure test sample to production and measured sound absorption coefficient. The test sample uses water-filled impedance tube built in this laboratory to carry out experimental measurement of the three-parameter calibration method. The results of finite element analysis and experimental measurement show that sound absorption coefficient of forward incidence is above 0.6 and backward incidence is below 0.2 in range of 3000 to 10000 Hz. And there is an obvious unidirectional transmission result from the forward and backward incidence, and the finite element simulation also obtains the same trend. Finally, through experiments and finite element simulation, it is proved the model has diode effect, indicating the design structure proposed in this study has potential for practical application.