Vibroacoustic Coupling of Cylindrical Structure with Both Excited End Plates
Vibroacoustic coupling phenomena occur in a variety of different situations and are generally studied with the goal of controlling noise. However, we also expect that they are applied to new technologies based on energy stored in each system. In this study, we investigate vibroacoustic coupling between structural vibrations and the internal sound fields of thin structures. We consider a cylindrical structure with thin plates at both ends and investigate the coupling between the plate vibrations and the internal sound field when external periodic forces are applied to respective end plates. This coupling is theoretically and experimentally investigated by considering the behavior of the both plates and the acoustic characteristics of the internal sound field with variations in the periodic forces. In the analytical model, the end plates are supported by springs in circumference to make those support conditions close to actual conditions in the experiment due to adjustments of spring stiffnesses, and then the cylinder is assumed to be structurally and acoustically rigid at the lateral wall between the structure and the sound field to simplify this problem. The acoustic characteristics are evaluated by the sound pressure level, which is maximized with changing the phase difference between the both plate vibrations, when the phase difference and relative amplitude between both periodic forces are varied. The behavior of the plate vibration is studied from changing the phase difference with the cylinder length. In comparison between characteristics of the both systems, it is clarified that vibroacoustic coupling is effective in increasing acoustic energy and the phase difference depends greatly on the acoustic mode, which contributes the formation of the sound field.
Fluid-Structural Coupling Of A Plate-Ended Cylindrical Shell: Vibration And Internal Sound Field
Abstract This paper presents a theoretical study of a plate-ended circular cylindrical shell radiating sound into its enclosed cavity. On the basis of a previously established free vibration model, a general formulation considering the full coupling between the subsystems (plate, shell and cavity) is developed. By using an artificial spring system, this formulation allows, in a systematic way, the consideration of a wide variety of boundary conditions and shell-plate joint conditions. Numerical results on the structure vibration and the generated sound field inside the cavity are presented. These results are intended to investigate two main issues: (1) obtaining a deep understanding of the coupling phenomena, which is a key factor to understand the mechanism of the mechanical energy transfer between the plate and the shell and mechanical-acoustical energy transfer from the structure to the acoustic medium; (2) illustrating the possibilities and limitations of sound-proofing by changing shell-plate joint conditions. The established model is believed to be useful in industrial applications where plate-ended shell structures are involved, especially in the case of the modelling of aircraft structures and fluid-containing industrial vessels.
Acoustoelasticity - General theory, acoustic natural modes and forced response to sinusoidal excitation, including comparisons with experiment
A comprehensive theoretical model has been developed for interior sound fields which are created by flexible wall motion resulting from exterior sound fields. Full coupling between the wall and interior acoustic cavity is permitted. An efficient computational method is used to determine acoustic natural frequencies of multiply connected cavities. Simplified formulae are developed for interior sound levels in terms of cavity, wall and external acoustic field parameters. Comparisons of theory and experiment show generally good agreement.