Study On Sound Isolation And Absorption Characteristics Of Sandwich Panels

Sandwich panel structures are usually composed of top and bottom panels and core structures.Due to their excellent mechanical properties,sandwich panels are widely used in aerospace engineering,marine engineering,high-speed trains,civil engineering and so on.With the increasing demand for the comfort of acoustic environment,the acoustic performance of sandwich panel has attracted more and more attention.In this paper,the theoretical derivation and calculation of sound transmission loss of orthogonal rib-stiffened sandwich panel and sandwich panel with pyramidal truss core are carried out,and the results are verified by experiment and finite element simulation.In addition,a new type of sound absorber of hybrid-arranged perforated panels is proposed,and the structure is also studied by theoretical,numerical and experimental methods.The main contents of this paper are as follows:The space-harmonic expansion method is applied to calculate the sound transmission loss of orthogonal rib-stiffened sandwich panels.The dynamic equations of the top and bottom face sheets are established by considering the tensional force,the bending moment and the torsional moment generated by the core.The amplitudes of the displacements are expressed as spaceharmonic forms.The vibro-acoustic coupling is considered by the continuity of normal velocity at the fluid-structure interfaces.The virtual work principle is applied to calculate the dynamic responses of the face sheets,and then the sound transmission loss is obtained.The equivalent dynamic mass density method is used to introduce the local resonator into the orthogonal ribstiffened sandwich panel so as to improve the dip of sound transmission loss consistent with the coincidence resonance frequency,and the design method of the local resonator is presented.The reliability of the theoretical results is verified by finite element simulation and experiment.The effects of different parameters of local resonator and the structure on sound transmission loss are analyzed.For the sandwich panel with pyramidal truss core,the connecting rod in the core is equivalent to spring,torsion spring and mass,and the dynamic equations of the top and bottom panels are established.The space-harmonic expansion method is used to calculate the sound transmission loss of the structure.Aiming at improving the sound transmission loss of sandwich panel under coincident resonance frequency,the concept of local resonance acoustic metamaterial is introduced,and the method of designing local resonator is given.By setting the objective frequency at the coincidence frequency,the acoustic performance of sandwich panel is improved.The influence of parameters of local resonator and the structure on sound transmission loss is discussed.Based on the theory of impedance of traditional perforated panel,a new type of sound absorber of hybrid-arranged perforated panels is proposed,in which the rigid partitions between the air back cavities are replaced by the perforated partitions to improve the sound absorption performance.The sound absorption coefficients of the structure are obtained by using equivalent circuit method,finite element simulation and experiment.The accuracy of the equivalent circuit analysis is validated,and it is proved experimentally that the introduction of perforated partitions can significantly improve the sound absorption coefficient of the absorber.