The Study on the Measurement of Material''s Underwater Acoustic Properties by Using the Water-filled Elastic Impedance Tube

• Main Authors: Zhi-Yu Jian, 簡志宇
• Other Authors: 謝傳璋
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/93764257080712251012

碩士 === 國立臺灣大學 === 工程科學及海洋工程學研究所 === 93 === The purpose of this study is to investigate the acoustic reflection coefficient of the underwater materials measured in a water-filled impedance tube. In the theory, some modifications are proposed to discuss the elastic waveguide inside the tube, assessing the feasibility of plane wave theory. Then, linear spring mathematic model is proposed. It is expected that the measured complex material impedance can be equivalent to three physical parameters, say, the equivalent “mass”, “spring stiffness”, and “damping coefficient.” Next, the three physical parameters can be recalculated to obtain the reflection coefficient, which further can be compared with the measured result to verify the feasibility of the suggested model. In the experimental process, free surface and materials are measured with impedance tube of different length and thickness. The result of free surface proves consistent with the theory. However, with longer and thicker tube, the measured result shows even more consistencies, with fewer errors.