Study On Acoustic Radiation From A Cylindrical Shell With An Internal Plate

Cylindrical shells used as model of submarine cabin, pipes, plate, airplane cabin, motorsare researched widely, especially for the underwater vehicle. It is important to reduce thenoise from the structure to strengthen its Concealment and survivability. In many cases theshell and the fluid which are in contact with each other have densities of the same magnitude.It is then impossible to neglect the coupling between the structure and the fluid surrounding orcontained in it. Many problems occur when the excitation frequency is close to aneigenfrequency of the structure. Because it is very difficult to take exactly into account exceptin a few cases which many researchers focus on. On the other aspect complex structures areresearched widely, from stiffed ring ribs to plate, from pure material to composite materials.This paper studies sound radiation from cylindrical shell with a internal plate. Firstly, theHelmholtz equation which describes the propagation of sound in fluid is derived, with theboundary between the shell and the fluid. Applying the Fourier transform, Hankel functionsand stationary phase method to the equation, the far-field sound pressure is solved. With thenumerical analysis methods, sound pressure level with an internal plate of multi-position andmulti-thickness is calculated. Moreover the sound radiation of finite cylindrical shell with aninternal plate is analyzed using FEM-BEM method. The results show the existence of internalplate strengthens the sound radiation and the relati8ve stiffness of shell and plate has asignificant influence on it. There are some Minimum values of sound pressure level withparticular relative stiffness which can direct the design for reducing the sound radiation of thestructure.