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Vibroacoustic modelling of enclosure coupled to a flexible wall with attached spring-mass-damper system

Mohd Noh, Mohd Firdaus (2015) Vibroacoustic modelling of enclosure coupled to a flexible wall with attached spring-mass-damper system. Masters thesis, Universiti Tun Hussein Onn Malaysia.

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Abstract

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.

Item Type: Thesis (Masters)
Subjects: T Technology > TA Engineering (General). Civil engineering (General) > TA349-359 Mechanics of engineering. Applied mechanics
Depositing User: Normajihan Abd. Rahman
Date Deposited: 03 Mar 2016 07:38
Last Modified: 03 Mar 2016 07:38
URI: http://eprints.uthm.edu.my/id/eprint/7547
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