ANALYSIS OF INTERIOR ACOUSTIC FIELDS USING THE FINITE-ELEMENT METHOD AND THE BOUNDARY-ELEMENT METHOD

For the first part of this study, the finite element method (FEM) and the boundary element method (BEM) are both used to predict the interio r acoustic field of a rectangular closed cavity, due to the vibration of one wall. The direct (i.e. inversion of the dynamic stiffness matri x) and modal superposition solution techniques are compared for the FE M, and the collocation and variational techniques are compared for the BEM. It is found that there are no significant differences between th e collocation and variational results. Identical results are also obta ined from both the direct and modal superposition techniques, provided that sufficient modes are included in the latter case. In order to in vestigate the influence of the boot (luggage) compartment on the acous tic response of the passenger compartment of a car, a second (smaller) rectangular cavity is joined to the one described above. The acoustic response of the combination is computed by the FEM when the two cavit ies are separated by different types of partition. It is found that ad dition of the boot cavity, as well as the characteristics of the parti tion, have a very marked effect on the main cavity response.