RADIATION OF SOUND INTO A CYLINDRICAL ENCLOSURE FROM A POINT-DRIVEN END PLATE WITH GENERAL BOUNDARY-CONDITIONS

The radiation of sound from a point-driven circular plate into a hard-walled cylindrical enclosure is investigated. Emphasis is given on studying the effects of the boundary conditions of the plate, which are modeled as a continuous distribution of edge springs acting against both the deflection and the rotation of the contour of the plate. With this model, both classical and intermediate boundary cases can be simulated by adjusting the elastic stiffness of the springs. A coupled acoustoelastic formulation is developed following a variational approach, with the use of hard-walled cavity modes. In the analysis, the full interaction between the structure vibration and the internal cavity sound pressure is considered. Numerical results indicate that a significant reduction in noise inside the cavity can be obtained for a relatively wide frequency range by completely relaxing the translational support (zero deflection stiffness) of the plate. This is mainly due to a weakening of the modal radiation efficiency of the flexural modes of the plate. With an increase of the deflection stiffness on the contour of the plate, this beneficial frequency range is shifted to higher frequencies. It is hoped that the findings of the present work will be useful for practical predictions of airplane cabin noise emitted by the rear pressure bulkhead, as well as for noise control in some aerospace structures and mechanical systems involving cylindrical-shaped cavities.