Influence of Internal Cavity in AIr-Borne Radiated Noise of an Underwater Structure

In this paper, the influence of internal cavity of an underwater structure was evaluated using an finite element(FE)/boundary element(BE) coupled model. For a cylinder-shape underwater structure, velocity sources were located in the internal cavity of the underwater structure. The underwater radiated noise due to the velocity sources was measured in order to obtain the air-borne underwater acoustic transfer function. Two numerical models that can simulate the underwater radiated noise using the FE/BE coupled formulation were contracted. In the first model, only the structure and exterior water medium were included in the FE/BE coupled model and a unit pressure was exerted on the wall of the internal cavity in order to calculate the acoustic transfer function. In the second model, the internal cavity was included in the FE/BE coupled model, and calculated average pressure in the internal cavity was used to simulate the acoustic transfer function. The calculated acoustic transfer functions were compared with that of measured one, and the differences were investigated to examine the influence of the internal cavity on the underwater radiated noise in the underwater structure.