Abstract: The structural-acoustic design model for an enclosed cabin section of underwater vehicle was built up using FEM/BEM method based on modal coordinates,the vibration and sound radiation characteristics were analyzed by this coupled design model for the simple supported finite cylindrical shell ended with rigid circular plates.The results were compared with that of substituting semi-infinite rigid cylindrical baffles for the rigid ci rcular plates.It demonstrates that as the perimeter of the outer cylindrical shell is smaller compared to the wavelength of sound in ambient fluid,the sound radiation law of the simple supported and stiffened double cy lindrical shell ended with rigid circular plates is similar with that extended by two semi-infinite length rigid cylindrical baffles,except the case that is near the natural frequencies of a few coupled modes.