ACOUSTIC RADIATION FROM A COUPLED PLANAR SEMI-COMPLEX STRUCTURE IN HEAVY FLUID

A mathematical model is derived to address the vibrations and sound ra diation into a dense fluid, of a coupled system consisting of two semi -complex plates (i.e., supporting added mass, stiffeners, and having a rbitrary elastic boundary conditions) linked in four points through mu ltistage suspensions elements. The supporting plate is subjected to po int, line or surface harmonic excitation, while the radiating plate is excited through the suspensions. Both plates are assumed to be baffle d, and the radiating plate is fluid loaded. The model is based on a va riational approach for the plates, and a matrix transfer approach is u sed to handle the coupling between the two-plates. The solution is fou nd using a Rayleigh-Ritz expansion in terms of polynomial trial functi ons which are shown to allow for the arbitrary elastic boundary condit ions and to facilitate the calculation of the radiation impedance matr ix. The vibrations and noise design of the system is discussed. The ma in design indicators are the force transmissibilities between the diff erent excitation and attachment points, the mean square velocity, the radiated power and the radiation efficiency of the radiating plate. Nu merical examples are presented to show the effects of fluid loading an d different design parameters (plates thickness, boundary conditions, added mass, stiffeners, etc.) on the radiated sound.