| The problem of sound radiation from shells of fluid-structure coupling is involved in many academic subjects. This is the advanced problem in the domain of structural acoustics. Cylindrical double-shell structure is the basic component. It is widely used in the engineering field. The research on these structures' underwater acoustic-vibration characteristic takes a significant role of theory and practicality in controlling project structures' noise and low noise optimizal design.Numerical method for calculating elastic structures' acoustic-vibration characteristic under water has the merit of adapting to various intricate models. Models' vibro-acoustic properties have been calculated by using FEM and BEM. The models are cylindrical double-shell structures with ribs and two-side baffleplates. By analyzing acoustic characteristic of each model in different case, the paper summarizes the laws of underwater vibro-acoustic characteristic of the cylindrical double-shell with changing factors, such as shell's thickness, rib's thickness, medium's continuing or not between shells and rib's quantities. The paper also summarizes the results of vibration and sound radiation from the cylindrical double-shell charged with water between shells with and without ribs, and from the ribbed cylindrical double-shell with air layer in the water between shells. Those three kinds of models' results indicate that the energy is mainly transferred through the fluid between shells at low frequency range and more energy will be transferred through ribs with frequency increasing. Generally, it is difficult to reduce vibration and noise at low frequency range. So, the results in paper indicate that if the energy transferred through the fluid between shells is depressed, the sound radiation from double-shell structures will be reduced enormously at low frequency range.This paper can provide some reference for low noise optimization design and noise control of similar shell structures in future projects.
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