An analytical calculation model and influencing factors for sound insulation of asymmetric sandwich plates

An approach for the prediction of the sound transmission through asymmetric sandwich plates is proposed.Through the calculation of the apparent bending stiffness of the asymmetric sandwich beam,the frequency-dependent bending stiffness of the corresponding sandwich plate is obtained,and by substituting the fourth-order governing equation,the sound transmission loss of asymmetric sandwich plate can be easily calculated by applying the modal expansion method.Four customized sandwich plates with carbon fiber sheets and polymethacrylimide core layer are compared through theoretical calculations and experimental tests.The error between the predicted and measured weighted sound reduction index is less than 3 dB in the frequency range of 100 Hz to 3150 Hz.The influences of symmetry of the sheets and the shear modulus of core on the sound transmission loss of sandwich plates are discussed.It is found that the shear modulus of the core has the most significant influence on the Transimission Loss(TL) when the surface density of the composite plate is constant.When the shear modulus of the core layer is small,the asymmetry of sheets results in a significant decrease in the coincidence frequency,which is also detrimental to the overall sound transmission of the sandwich panel.