Overview of Structural-Acoustic Modal Analysis Under Random Loading

Random excitations can result from various types of non-deterministic loads such as wind loads, terrain loads, and other types of white noise loads. In this paper, an overview is presented of the modal method to obtain the random response of a coupled structural-acoustic system subjected to random excitations. When the structural system is coupled with an enclosed cavity, the structural-acoustic frequency response functions (FRFs) can be obtained using the uncoupled structural modes and the uncoupled acoustic modes, with structural-acoustic coupling as well as modal damping included in the formulation. The random response of the coupled structural-acoustic system is then obtained by summation of the structural-acoustic FRFs with the applied auto- and cross-spectral random loadings at the excitation locations. The theoretical formulation of the coupled structural-acoustic system is described. An example of a rectangular cavity coupled with flexible panels exposed to external random white noise load is presented. The methodology is then applied to an automotive vehicle travelling over a randomly rough road to predict the interior sound pressure response in the vehicle.