Prediction of Noise Transmission through Honeycomb Sandwich Panels Using a Wave and Finite Element Method

This paper describes an application of a wave and finite element (WFE) method to the prediction of the low-frequency sound transmission loss (STL) of infinite honeycomb core panels. At low frequencies, when the dimensions of the periodic cells of the structure are small compared to the structural wavelength and acoustic wavelengths, the periodicity effect can be "smeared" out. The honeycomb sandwich panel can then be modelled as a continuous structure. The WFE method starts with meshing a 3-D periodic cell of the structure using a conventional finite element (FE) method. The size of the FE model of the periodic cell can be reduced using a Component Mode Synthesis (CMS) method. For a given frequency, a reduced dynamic stiffness matrix is found. Wave propagation in the fluids surrounding the structure is modelled analytically. By post-processing the matrix using periodic structure theory, a spectral dynamic stiffness matrix is derived to calculate the response to an incident acoustic wave. Excitation of the structure by oblique plane waves and a diffuse sound field are both considered. Numerical examples are presented to illustrate this approach. The WFE model can give accurate predictions at small computational cost.