Sound Propagation Characteristics of Porous Materials Lined with Partitions

• Main Authors: Juan, Chien-Fu, 阮建富
• Other Authors: Wang, Chao-Nan
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/82502171228327655234

碩士 === 國立臺灣大學 === 造船及海洋工程學研究所 === 90 === 　　The objective of this research was to discuss the absorption coefficient and transmission loss of porous materials lined with partitions. In the thesis, we used Biot’s theory of elastic waves propagating in a fluid-saturated porous solid and the transfer matrix of porous material introduced by Allard, to evaluate the absorption coefficient and transmission loss of multi-layers media of porous materials and partitions. 　　In the experiments, we proved the accuracy of this model by measuring the transmission loss of single aluminum plate lined with porous material. Our results indicated that in the aspect of sound absorption in porous material, increasing the thickness of the layer could rise the absorption coefficient in the low frequency range; as to multi-layers media, porous material with higher density placed on the surface of sound incident side would have a better effect of absorption. In the aspect of sound transmission, increasing the density and thickness of porous material could rise the transmission loss. However, we had to notice the transmission loss drops due to coincidence effect of bonded material in the study. Material unbonded (i.e. assumed an air gap between the aluminum and the porous material) would have a higher transmission loss than the bonded one in the high frequency range.