Application of a wavenumber domain numerical method to the prediction of the radiation efficiency and sound transmission of complex extruded panels

Complex-shaped aluminium panels are adopted in many structures to make them lighter and stronger. The vibro-acoustic behaviour of these complex panels has been of interest for many years but conventional finite element and boundary element methods are not efficient in predicting their performance at higher frequencies. Where the cross-sectional properties of the panels are constant in one direction, which is the case for extruded panels, wavenumber domain numerical analysis can be applied and this becomes particularly suitable for panels with complex cross-sectional geometries. Because they are based on a two-dimensional model, these methods can reduce the computational cost compared with other numerical methods using full three-dimensional models, while nevertheless including three-dimensional effects. In this paper, a coupled waveguide finite element and boundary element method is applied to predict the radiation efficiency and sound transmission of a double-layered aluminium extruded panel from a train carriage floor. The results are interpreted in the wavenumber domain from which the contributions of different types of waves can be identified. In the calculations, the air cavities between top and bottom panels are considered to examine their contributions to the vibro-acoustic behaviour of the panel. The predicted results are compared with measured ones obtained using a finite length panel. To reflect the finite length of the actual panel used in the measurement, spatial window functions are applied to the sound transmission through the infinitely long panel, giving improved agreement with the measurements.