Research On Predictive Method For Mechanical Noise Of Underwater Vehicles

The underwater vehicle usually means underwater weapon system such as submarine, torpedo and so on. The level of mechanical noise of underwater vehicles is one of main index of strategy and tactic in acoustic warfare, which restricts battle effectiveness and survivability. Therefore some developed countries emphasized on the optimized design and noise control of the underwater vehicles. The prediction for structural noise that is the base of low-noise design provides the referential parameters and the direction for the optimized design and noise control, therefore it is necessary to make research into mechanical noise of underwater vehicles.There are mainly two parts in this paper, the study of mechanism and characteristic of mechanical noise source of underwater vehicles, on which based method of mechanical noise prediction by the way of theoretical analysis and experimental research. The prediction of structural noise largely includes exciting source, vibration transmission and acoustic radiation of shell of underwater. The exciting sources primarily indicate mechanical vibration of engine; the vibration transfer from machine to the shell through the isolation device, and the surface impedance of the foundation are concerned. Stiffened cylindrical shells are major structure of motive cabin of submerged vessels, and the vibration and acoustic radiation of other cabin regularly decrease. As for the different frequency band that should be analyzed , we should use the appropriate predictive method and model respectively.Using mode analysis method and theory which can be used to analyze the frequency band range below the ring frequency, the prediction of mechanical noise of underwater vehicles , the radiated sound power ,the surface average velocity and the radiation efficiency are present. An average square acceleration method and radiation efficiency based on statistical energy analysis (SEA) is presented in this paper, which analyze input impendence, vibration characteristics and sound efficiency, at the same time the level of mechanical noise power and pressure are concerned above the ring frequency . Finally, this paper predicted the noise of some underwater vehicle by using noise prediction model, which is satisfactory.In sum, by theoretical analysis and experimental research, this paper not only establish comparatively applicable predictive methods and models, but also can give some helpful and useful information for the optimized design and noise control of the underwater shell-structure. So the study of this paper has very important significance for the appliance in the underwater acoustic engineering field.