Calculation of Aero-Acoustics Transmission Loss for Micro Perforated Panel (MPP) Muffler Inside A Hush-House Chamber

• Main Authors: Tian-zi Eng, 黃田子
• Other Authors: Yung-Tang Shen
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/30706351060778356965

碩士 === 朝陽科技大學 === 建築系建築及都市設計碩士班 === 101 === Micro Perforated Panel (MPP) has tiny pores which attenuates sound decay based on the Helmholtz resonance. It can be used in various sizes of industrial muffler pipe and mechanical purposes, such as motor vehicles, air conditioner, exhausting pipe, etc. Generally, the sound absorption coefficient of the MPP was predicted by Maa (1975). It has been able to obtain the sound pressure coefficient by measuring method or simulation. However, the calculation of sound transmission loss(STL) becomes more complicate when a panel surface is with a thermal flux. Munjal (1986) proposed the computation method of air conditioner pod silencer. In addition, Munjal(2003) also proposed a simplified formula of MPP. Nevertheless, the formula is only approach measure values in low frequency but it is unable to calculate the section of high frequency in the pod silencer. Therefore, this study is to explore strategy for evaluating the aero-acoustics transmission loss for MPP inside a T-10 Hush-House chamber. It’s proposed to favorably the thermal flux and importing the air conditioning as well as eliminates the noise sources. Therefore, the regulation of calculation is in three items: 1.Dimension of the anechoic chamber. 2. Different scales of MPP. 3. The environmental conditions of the anechoic chamber. This study applies the formulation of the boundary element method (BEM) in transfer matrix for the process of theoretical derivation to achieve the simulation of STL through a MPP. Finally, this study finds that 1. The direction of wave number 〖(K〗_(z,m)) takes a significant factor to control the impedance of material and spatial. 2. The proper calculation of the high frequency is in order to wave number〖(K〗_(z,m)) of each frequency velocity direct to material density. 3. The favorable proportion of anechoic chamber at T-10 Hush-House is between 3 and 4 by S/P.