Research On Transmission Of Vibratory Noise In Acoustic Covering Layers Of Ship

Acoustic cover layers is an important ship of underwater acoustic materials and structures, laying on the surface and the fore-body sonar platform. It can absorb the detecting waves of the enemy active sonar, reducing the submarine acoustic target strength; at the same time, it can inhibit the submarine body vibration, reduce the outside noise generated by mechanical vibration except the propulsion system, and decrease the intensity of signal radiation characteristics of the submarine target. Wedge is widely used in surface ships. Although the research about acoustic cover layers of the sound field theory has a rather long history, so far there is no depth research of sound wave in the acoustic cover layers of the transmission characteristics.This thesis researches the submarine vibration and noise in the acoustic cover layers of the transmission characteristics deeply from theory analysis, wedge experiment,numerical calculation.The main content of the thesis is as follows :Firstly, the transmission theory of sound wave in the acoustic cover layer structure is researched ,and it is ameliorated and corrected on the base of non-uniform wave guide theory .There is special consideration of the cavity air wedge acoustic absorption properties of the structure. The thesis studies the sound absorption performance of wedge acoustic covering layers through experiment, the results of sound absorption coefficient of wedge acoustic covering layers calculated in the thesis are compared with actual measured data.Secondly, application of the sound absorption performance thesis of taking into the air of cavity in the hull acoustic cover layer ,the thesis studies the sound absorption performance of wedge acoustic covering layers.The material dynamic mechanical parameters, density and wastage gene of acoustic covering layers are considered. The thesis studies the sound absorption performance of wedge acoustic covering layers in the different cavity structure with the numerical and experimental method.Thirdly, by using half-numerical and half- experiment method, the performance of the wedge acoustic cover layers in the different application environments is analysed.The thesis studies the sound transmission performance of wedge acoustic covering layers in the different hydrostatic pressure, and temperature surrounding.Fourthly, distribution of self-noise on fore-body sonar platform is predicted by using numerical method, and the effect of sound characteristic with different work conditions is researched. The infection of vibration response and radiation noise of the fore-body sonar platform structure with the wedge acoustic cover layer is reseached.