Abstract: Aiming at a frigate model based on the DTMB 5415 hull form, a coupled sound field calculating method for ship underwater radiation noise in low-middle frequencies was discussed by considering three typical categories of vibration and sound sources, mechanical, propeller and hydraulic noise. A vibroacoustic coupling FEM-IBEM (the finite element method-indirect boundary element method) model for the frigate was established, and the front 40000 order modes were calculated as the modal basis for the acoustic response. This study then calculated the acoustic radiated power level in 0-500Hz and analyzed directional properties and spectral characteristics for every noise component, and it compared the differences between the direct superposition and the coupled sound field calculating methods. The research shows that the physical model of the coupled method is more exact and efficient, and it is a preferred method for ship underwater radiation noise numerical prediction in low-middle frequencies excited by multiple categories of vibration and sound sources.

Key words: ship underwater noise, hydraulic noise, mechanical noise, propeller noise, coupling acoustic fields, sound power