The design and analysis of acoustic broadband absorptive surface using resonance

• Main Authors: Jen-TingHuang, 黃任廷
• Other Authors: I-Ling Chang
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/54bbr8

碩士 === 國立成功大學 === 機械工程學系 === 106 === In this study, an improved acoustic broadband absorptive surface was proposed and investigated. The impedance chamber system was built to measure the absorption of the designed structure. We used the impedance matching theory to calculate the surface acoustic impedance and sound absorption for different types of tube absorbers, and numerical simulation was performed to examine the applicability of the impedance matching theory. It was found that the absorption of the absorbing tube would not change a lot by changing the cross-section shape from circular to square. The absorption peaks were caused by the resonance inside the tube and the acoustic energy was dissipated by the air viscosity. By introducing the folding tube, it was also discovered that the higher absorption peak frequency would shift if we increased the folding number. These findings were confirmed both numerically and experimentally. Lastly, we proposed an acoustic broadband absorptive surface design by combining parallel and serial tubes with foldings to save space while maintaining high absorption over a wide range of frequencies.