Research On Acoustic Vibration Characteristics Of Honeycomb And Foam Sandwich Plates

Sandwich structures have the advantages of light mass,high specific stiffness and specific strength,and are widely used in vehicles,rail transportation,aerospace,and construction.Although sandwich structures have many advantages,sandwich structures with honeycomb and foam cores are more susceptible to radiated noise due to their light mass and excitation.Therefore,accurate and efficient structural sound transmission calculation methods are very important to master the key acoustic parameters in the design process of honeycomb and foam sandwich panels.In this paper,the theoretical derivation of the sound transmission losses of typical sandwich panels in diffusive sound fields is carried out from the higher-order differential equations of bending vibration of sandwich panels with the background of light-weight structural applications in high-speed railway carriages,focusing on the influence of the sound radiation term on the sound transmission losses,and also the analytical study of the sound radiation characteristics of sandwich panels under linear force excitation.The main research contents of this paper are as follows:(1)Starting from the higher order differential equations of bending vibration of honeycomb and foam sandwich panels and based on the modal superposition,a method is proposed to calculate the sound transmission loss of honeycomb and foam sandwich panels in the diffuse sound field.The calculated values of the theoretical model are compared with the experimental results to verify the correctness of the prediction model,and the effects of the shear modulus,thickness and loss factor of the core layer on the sound transmission loss of the sandwich panel are further investigated.Compared with Virtual.Lab simulation software,the model can significantly improve the computational efficiency.(2)The influence of the acoustic radiation term on the sound transmission loss of single-layer and sandwich panels was analyzed.The difference between the sound transmission loss under the conditions of considering the acoustic radiation term and ignoring the acoustic radiation term was calculated,and the effects of factors such as core shear modulus,surface density and core thickness of sandwich panels on the difference were analyzed numerically.It was found that,unlike single-layer or heavily damped sandwich panels,the sound radiation term of lightweight sandwich panels has a greater effect on the sound transmission loss of the panels at the coincident frequency.For the prediction of sound transmission loss of honeycomb and foam sandwich panels,the acoustic radiation term cannot be neglected,and the maximum difference of sound transmission loss is 7 d B with an average difference of 3～4 d B when considering or not considering acoustic radiation.(3)The equations for the mean square vibration velocity and acoustic radiation power of honeycomb and foam sandwich panels under the condition of linear force excitation were derived.Compared with single-layer panels of the same surface density,the response and acoustic radiation power of sandwich panels under line force excitation are significantly smaller than those of single-layer panels below the first-order resonance frequency of sandwich panels;above the first-order resonance frequency of sandwich panels,the response of sandwich panels is smaller than that of single-layer panels,but the acoustic radiation power is slightly higher than that of single-layer panels.In addition,the influence law of panel material,core layer thickness and core layer loss factor on the acoustic radiation characteristics of sandwich panel was also explored.