The Vibration & Acoustic Radiation And Noise Muffling Characteristics Of Plate Structures

With the development of technology, the enhancement of people' living standard and the need of military strategy, the problem of ship noise controlling has received an increasing attention. Many kinds of plates have been used in engineering fields, which not only can radiate acoustics under the outside implement but also can be used in noise controlling. Damping technology is a very effective way to dispose of vibration and noise problem. At present, it has been extensively utilized in many areas, such as aerospace, machinery and shipping, etc., which can lower the ability of structural vibration and acoustic radiationIn this paper, firstly an acoustic model and the relation between acoustic power and vibration velocity are established, FEM calculating results reveal that stiffener can lower the face vibration velocity and the radiation acoustic power. Besides, eigenvalue analysis is used in sound-impedance matrix. With the help of optimization theory, the conclusion is received that the radiation efficiences by a group of velocity distribution corresponding to eigenvector are proportional to the eigenvalue of the velocity vectors.Secondly, the lame equation is used to model the motion of the free-layer damping. The motions are expanded in the depth direction. The continuous conditions of stress and displace at the layer's inter face are used. The structural loss factor is presented.Thirdly, considering when acoustic wave with a certain frequency or angle is incident upon plates, it will greatly cause the radiation power' translating. This paperdetails the causes of coincident effect and gets the calculating formula. Theconclusion is resulted that thick plate and uniaxial anisotropies can lower critical frequency.On the basis of above parts, this paper discusses the noise muffling of several kinds of plates. It gives the modifying formula of the mass law and verifies its accuracy with an example. At last, this paper explains the effect of stiffeners and damping on the plates' muffling characteristics.