Vibroacoustic modelling of enclosure coupled to a flexible wall with attached spring-mass-damper system
Generally, solutions to improve the vibration and noise problems are to redesign or modify the system such as increasing the thickness of the wall panels, enhancing the elasticity of the structure, and increase the damping mechanism of the structure. In this study, the application of vibroacoustic m...
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| 格式: | Thesis |
| 出版: |
2015
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| 主题: | |
| 在线阅读: | http://eprints.uthm.edu.my/7547/ http://eprints.uthm.edu.my/7547/1/MOHD_FIRDAUS_BIN_MOHD_NOH.pdf |
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| 总结: | Generally, solutions to improve the vibration and noise problems are to redesign or
modify the system such as increasing the thickness of the wall panels, enhancing the
elasticity of the structure, and increase the damping mechanism of the structure. In
this study, the application of vibroacoustic modelling of enclosure coupled to a flexible
wall was investigated and its effectiveness was further researched by attaching
single and multiple spring-mass-damper (SMD) system for the structural vibration
control and sound pressure attenuation. The SMD system is designed to minimize
the sound pressure amplitude of a flexible wall of a rigid walled enclosure. The sound
pressure characteristics of rigid walled enclosure, such as natural frequency and mode
shape were determined using two approaches which are simulation (ANSYS®) and
theoretical (MATLAB®). In the preliminary study, the theoretical equation derived in
MATLAB® such as rigid walled enclosure coupled to flexible wall and rigid walled
enclosure with attached SMD were used to validate finite element analysis (FEA) conducted
using ANSYS®. The result indicates that the theory and FEA showed in a good
agreement. Thus, proved that the FE model was accurate and can be applied in the
subsequent analysis. As the mass and damping of the SMD were changed, the sound
pressure of enclosure was also affected. The study showed that with attached SMD to
a flexible wall, the sound pressure of enclosure was dropped significantly. From these
result, single SMD with mass of 20 kg and damping coefficient of 10Ns/m provides the
best option. As the study extended to multiple SMDs attachment at different location
and configuration, the outcomes showed that the center point attachment on flexible
wall at coordinate (1,0.25,0.15) and the combination between location one, two, three
and four produce the highest reduction. Finally, it can be concluded that multiple
SMDs were able to reduce the sound pressure compared to single SMD. However, for
the structures that take weight into consideration, such as in aerospace, automotive and
machine system, adding numbers of SMDs will result excess weight to the structure,
thus reduce fuel efficiency. |
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