Path Identification On Vibration And Noise Source Of Underwater Complex Mechanical Structures

As far as we know sound wave is the only carrier which can efficiently transmit information in long distance water. Concealment of submarine can promote combat capability and is also the key of combat. Submarine cruise generally in low speed and then the mechanical equipment and its connection structure radiates noise into water through vibration.This kind of noise is the main noise source compared to the propeller noise and hydrodynamic noise. Mechanical structure-borne noise is produced by all kinds of mechanical equipment in the submarine which was transferred to the shell of the submarine through the shock absorber,base, partition, piping systems inside the submarine, and it radiates to the far-field to form the radiated noise. The study of mechanical structure-borne noise’s transfer through different paths is of great significance to control the noise’s propagation from source to radiation field and improve the submarine acoustic stealth performance. It’s also the current hot research problem in noise control field.In this paper, the process of transfer from the internal machinery and equipment to the shell vibration through different of paths is modeled. As the traditional transfer path analysis is accurate but computationally complex problem, operational transfer path analysis method can ensure the accuracy and greatly reduce the computation time. By introducing of transmissibility function matrix, which can avoid the FRF and incentive force load of complex, only use the operational input and output data to compute it. Optimizing it when the signal matrix occurs morbidly which can make further improving accuracy. Using coherence analysis to judge the coherence relationship between input and output signals. As there have much interference in the vibration signal it’s always use partial coherence analysis to eliminate the coherent component. The completeness of the input points is verified by computing the multiple coherences of the input points whether all sources are taken into account.On the submarine cabin model test platform, the experimental study of vibration transfer path analysis is proceeded. By means of operational experimental data validate operational transfer path analysis to be reasonable and analysis signal’s power spectrum and energy in the frequency domain. Each transfer path is analyzed while vibrations transmit to the shell from mechanical device. Combined with the proposed contribution analysis method calculates the contribution of each target point. By binding to the transfer characteristic comparison, we can determine that whether the contribution is caused by large transfer characteristics or high path excitation which can specifically target vibration and noise reduction processing.