本研究依據ASTM (2006)設計規範並應用三參數校正法，發展出可用來量測材料在水中的聲波反射與透射係數的直立式充水阻抗管。本研究所發展的充水阻抗管分為下管與上管兩部分，並於兩管之間裝設套管及上下夾片，作為置放受試材料處之用。為了測試所發展的阻抗管量測系統，本研究首先在三個不同天量測自由液面聲波反射係數，所得反射係數振幅相當一致，主要介於0.98到1.02之間，與理論值1.0非常接近，顯示本研究所發展的充水阻抗量測系統在量測反射係數方面，具有很好的準確性與可重複性。此外，為了驗證利用本研究所發展的阻抗管量測材料所得的反射係數具可重複性，本研究也於下管中，在三個不同天量測一橡膠多孔性複合材質試片的反射係數，包含其振幅及相位，結果顯示三個不同天所得反射係數的值非常接近。接著本研究在阻抗管中量測聲波通過上述材料試片的反射係數及透射係數，分別以同一天三不同時段以及三個不同天進行實驗的方式，測試實驗結果的可重複性。上述不同實驗所得反射係數及透射係數結果重複性皆非常高。此外，文中亦比較了受試材料其後端介質分別為空氣以及水時，反射係數的差異。上述實驗結果顯示本研究所開發的充水阻抗管可用來量測材料在水中的聲波反射與透射係數。

Based on the standard ASTM test method (2006) and the three-parameter-calibration method, in this study, a vertical water-filled impedance tube is developed for the purpose of measuring the acoustic reflection and transmission of materials. The impedance tube consisted of a lower and an upper tube, and a pipe casing with upper and lower clips was used to combine the two tubes and to install the test material. First of all, the developed impedance tube was used to measure the sound reflection coefficient near the free surface in the lower tube on three different days. The measured values showed good repeatability and ranged from 0.98 to 1.02, which was very close to the theoretical value of 1.0. A test sample made of porous rubber was also installed in the lower part of the impedance tube for the purpose of studying its acoustic reflection coefficient. The results obtained from the experiments carried out on three different days showed good repeatability in terms of both amplitude and phase. Finally, the reflection and transmission coefficients in the form of sound propagation through the test sample were measured, either three times on the same day, or once on three different days. Both the measured reflection and transmission coeffi-cients had high repeatability. Furthermore, the effects of the back-side medium of the test sample, either air or water, are briefly discussed. The experimental results demonstrate that the developed impedance measuring system can be used to obtain the underwater acoustic reflection and transmission coefficients of materials.

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