Abstract
Paper 1
The problem in which a flexible structure interacts with an acoustic fluid is analysed by use of the finite element method. With increasing complexity of the geometry and when increasing the frequency limit is of interest, the number of degrees of freedom needed to describe the system becomes very large. To reduce the coupled system, modal analysis is performed in the structural and in the fluid domain separately. The uncoupled eigenvectors are then used to reduce the coupled problem. A method for choosing which uncoupled eigenvectors to include in this operation is derived, further reducing the system. A numerical example is provided, demonstrating the efficiency of the method.
Paper 2
The unsymmetrical eigenvalue problem involved in analysing structureacoustic problems by use of the finite element method with a pressure formulation in the
fluid domain can be reduced through transforming it into a symmetric standard eigenvalue problem. The paper shows that when hysteretic damping is introduced in both the structural and the fluid domain, the problem can still be treated as a symmetric standard eigenvalue problem, which becomes complexvalued due to the damping.
Paper 3
This paper, which is based on the results reported in Paper 1 and 2, describes the implementation of structureacoustic finite element analysis in an integrated modelling environment, one which has interfaces to programs for meshing and for finite element analysis. The aim is to determine the vehicle interior noise on the basis of the force applied to the structure. An interface to a code developed for performing structureacoustic analysis involving coupled modal analysis and
frequency response analysis, is created. The possibilities this modelling environment provides are demonstrated. Use of this approach simplies cooperation between researchers and their interaction with industrial groups.
Paper4
Double leaf walls consisting of sheetmetal wall studs covered with plaster boards are studied. Acoustic behavior in the low frequency range is evaluated, aimed at determining the influence of the wall properties on sound reduction.The wall parameters studied are wall thickness, the number of plaster boards used, the stiffness of the wall stud web, and the boundary conditions.The influence of the dimensions of the connecting rooms is also studied.It is concluded that in the low frequency range the sound reduction a wall achieves can only be predicted by studying the actual roomwallroom conguration in question.
The problem in which a flexible structure interacts with an acoustic fluid is analysed by use of the finite element method. With increasing complexity of the geometry and when increasing the frequency limit is of interest, the number of degrees of freedom needed to describe the system becomes very large. To reduce the coupled system, modal analysis is performed in the structural and in the fluid domain separately. The uncoupled eigenvectors are then used to reduce the coupled problem. A method for choosing which uncoupled eigenvectors to include in this operation is derived, further reducing the system. A numerical example is provided, demonstrating the efficiency of the method.
Paper 2
The unsymmetrical eigenvalue problem involved in analysing structureacoustic problems by use of the finite element method with a pressure formulation in the
fluid domain can be reduced through transforming it into a symmetric standard eigenvalue problem. The paper shows that when hysteretic damping is introduced in both the structural and the fluid domain, the problem can still be treated as a symmetric standard eigenvalue problem, which becomes complexvalued due to the damping.
Paper 3
This paper, which is based on the results reported in Paper 1 and 2, describes the implementation of structureacoustic finite element analysis in an integrated modelling environment, one which has interfaces to programs for meshing and for finite element analysis. The aim is to determine the vehicle interior noise on the basis of the force applied to the structure. An interface to a code developed for performing structureacoustic analysis involving coupled modal analysis and
frequency response analysis, is created. The possibilities this modelling environment provides are demonstrated. Use of this approach simplies cooperation between researchers and their interaction with industrial groups.
Paper4
Double leaf walls consisting of sheetmetal wall studs covered with plaster boards are studied. Acoustic behavior in the low frequency range is evaluated, aimed at determining the influence of the wall properties on sound reduction.The wall parameters studied are wall thickness, the number of plaster boards used, the stiffness of the wall stud web, and the boundary conditions.The influence of the dimensions of the connecting rooms is also studied.It is concluded that in the low frequency range the sound reduction a wall achieves can only be predicted by studying the actual roomwallroom conguration in question.
Original language  English 

Qualification  Licentiate 
Supervisors/Advisors 

Place of Publication  Lund 
Edition  1 
Publisher  
Publication status  Published  2001 Dec 
Subject classification (UKÄ)
 Fluid Mechanics and Acoustics