ABSTRACT
Finite Element Analysis (FEA) is a numerical method that can be used to calculate the response of a complicated structure due to the application of forcing functions, which could be an acoustic source or a distribution of mechanical forces. FEA can also be used to estimate the sound power radiated by a structure or the distribution of the sound field in an enclosed space. Estimating the sound power radiated by a structure into an acoustic region generally requires a large numerical model and the associated computer memory requirements are large. An alternative is to use FEA to calculate the vibration response of the noise-radiating structure only and then use a numerical evaluation of the Rayleigh Integral to calculate the radiated sound power. Alternatively, if the structure is excited by an external sound field, then FEA can be used to determine separately the in-vacuo (i.e., without the acoustic fluid) structural
response as well as the resonance frequencies and mode shapes of the rigidwalled enclosed sound field. Then the actual sound pressure distribution in the enclosed space can be calculated using modal coupling analysis implemented with a programming tool such as MATLAB. Software for conducting this type of analysis is described in Appendix C. The underlying theory for FEA is covered in many textbooks and will not be repeated here. However, its practical implementation using a commercially available FEA package will be discussed in an attempt to help potential users apply the technique to acoustic analysis. Finite element analysis of acoustic systems involves the discretization of the acoustic volume into elements and nodes. An enclosed acoustic volume might be surrounded by rigid-walls, a flexible structure, or walls that provide acoustic damping. Alternatively, the acoustic radiation of a structure into an anechoic or free-field can also be examined.
