A numerical study of the soundproof performance with rubber pillar structure
Date Issued
2015
Date
2015
Author(s)
Chen, Tai-Cheng
Abstract
The compatriots have paid attention to the promotion of life quality in recent years. And the noise is a type of negative factor reducing the quality of life. To the machine tool operator, the noise even induces the occurrence of the employment injuries. So designing a good soundproof structure to reduce the intensity of the noise and further enhancing the working quality of operator are urgent issues. The thesis utilizes the finite element analysis software ”COMSOL Multiphysics” to simulate a plane wave going through pillar rubber structural plate , and investigates the difference of loudness between the sound wave and the observation surface, for varied column heights. Conducting eigenfrequency analysis on the column plate can acquire the resonant and anti-resonant frequencies for some column heights. Then using the frequency analysis can learn the sound pressure levels for the observation surface corresponding to resonant and anti-resonant frequencies. The object of this study is the leaf blower in the campus of National Taiwan University. First, we take advantage of the sound recorder to record the sound coming from the leaf blower during operation. Then, by the program based on fast Fourier transform, we can acquire the Fourier coefficients corresponding to each frequency. To express the total energy the listener receives instantaneously, we conduct the ‘A’ frequency weighting function on the average pressure of the observation surface in frequency range 20~20kHz for the intervals of 1Hz. And then we sum the loudness corresponding to each frequency. Finally we acquire the numerical decibel of the observation surface for different height of the pillar plate. We can find that the case of hc=11mm has the best ability to reduce the decibel in the eleven cases. Adjusting the value of hc can change the anti-resonant frequency, and then block certain frequency in the range of 4905Hz-5967Hz. Finally we find that the case of hc=19.8425mm can reduce 92.397dB at 3370.17Hz.
Subjects
soundproof
finite element analysis software
pillar plate
fast Fourier transform
‘A’ frequency weighting function
Type
thesis