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A FINITE ELEMENT APPROACH FOR CALCULATING SOUND PRESSURE LEVEL IN A COUPLED STRUCTURAL-ACOUSTIC SYSTEM

Dr. Akbar Eslami Associate Professor Technology Department Elizabeth City State University Elizabeth City, NC 27909

Abstract

In this study, the sound-structure interaction problem in a coupled structural-acoustic system has been investigated. The novelty of this investigation is embedded in using of Finite Element Method to calculate sound pressure level. The governing differential equation for the interaction of the acoustic cavity with the flexible wall (plate) is calculated. The modal analysis of such a problem is possible, an analysis in which the decoupled equations of motion for the cavity and the flexible wall can be obtained separately. In order to accomplish this task, the coupled structural-acoustic system has been decomposed to an acoustic component, a cavity with a rigid wall, and a structural component, a flexible wall (plate). The cavity modes (eigenvalues and eigenvectors) of the cavity with the rigid wall boundary condition and structural modes of the simply supported flexible plate in a vacuum are obtained by using the finite element method. The coupled structural-acoustic equation for the pressure inside the cavity is obtained in terms of the eigenmodes of the cavity and the flexible wall. The coupling method has been successfully implemented into two classical existing problems.

1. Introduction

Interaction between the internal sound pressure field and the flexible wall of an enclosure has been a very popular subject for scientists and researchers. The results of such interaction will induce an acoustic pressure and noise field that poses a major engineering design challenge. Therefore, a good understanding of the mechanisms of noise transm ission through an elastic plate allows us to use more effective techniques to control noise. Consider a fluid in a cavity which has a surface such that part of the surface is flexible (Fig. 1). The flexible wall is excited by external pressure in which int eraction between the flexible wall and the fluid in the cavity has an impact on the acoustic pressure within the cavity. Due to vibration of the flexible wall, an acoustic pressure will be generated in the coupled structural-acoustic system. Various approaches have been developed by different researchers to calculate the interior pressure in a coupled structural-acoustic system1-7. In this study, a modal coupling method is adapted to determine the acoustic pressure. In this method, the coupled structural-acoustic system has been decomposed to the acoustic component, a cavity with a rigid wall, and a structural component, a flexible wall (plate) with simply supported boundary condition. The acoustical modes are obtained by mathematically combining the cavity modes and the structural

“Proceeding of the 2002 American Society for Engineering Education Annual Conference & Exposition Copyright © 2002, American Society for Engineering Education ”

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Eslami, A. (2002, June), A Finite Element Approach For Calculating Sound Pressure Level In A Coupled Structural Acoustic System Paper presented at 2002 Annual Conference, Montreal, Canada. 10.18260/1-2--11291