以阻抗管法測量薄膜結構之等價MCK之研究

Abstract

本論文內容為以阻抗管法測量薄膜材料之反射係數，藉此推算此薄膜之等價質量、阻尼、彈簧係數。若是在薄膜後方緊貼硬板，則薄膜之特性無法顯現，也就難以計算等價質量、阻尼、彈簧係數。故本文在薄膜後方加上一個空氣腔體，藉此讓薄膜在特定的頻率範圍的特性得以顯現。為了驗證此方法的可行性，本文以等價質量、阻尼、彈簧係數重新計算得到的反射係數與阻抗跟實驗測得的反射係數與阻抗做比較，同時觀察更換不同腔體時計算出的薄膜材料之等價質量、阻尼、彈簧係數是否一致。最後測量薄膜之質量與等價質量做比較，觀察是否有相關性。本文對兩種薄膜進行測量，測得的等價質量、阻尼、彈簧係數，反算反射係數跟實驗測得的反射係數趨勢是一致的。簡單的驗證以等價質量、阻尼、彈簧係數模擬薄膜性質的可行性。

The purpose of this study is to use the impedance tube method to measurement the reflection coefficient of membrane-structure. Then, using the reflection coefficient to calculate the equivalent MCK of membrane-structure. If we put the membrane close to a hard board(assume rigid), The membrane's characteristics is difficult to show. So we add a cavity on back of the membrane to make membrane's characteristics show. In order to verify the feasibility of this method. Use the equivalent MCK to calculate the reflection coefficient and impedance, then compare with the experimental data. At last, We compare the equivalent mass and real mass to observe whether there is a correlation. This thesis measure two membranes. We find the trend is the same, between reflection coefficient and impedance calculating by equivalent MCK and experimental data.