Anisotropic and sandwich structures are used in many engineering areas such as aerospace and automotive constructions. These types of structures are often used because of their high stiffness to mass ratios. However these structures oftentimes present a compromise between their mechanical and vibro-acoustic behaviour. The vibro-acoustic study for the anisotropic and sandwich structures is well developed during the last years.

There are many methods which allow the computation of the wavenumbers for isotropic and anisotropic structures. Analytical formulas exist to calculate the wavenumbers of anisotropic plates based on the Classical Laminate Plate Theory. To take into account shear deformation, Whitney suggested the formulation of the First-order Shear Deformation Theory (FSDT). A model for an infinite sandwich panel by including the description of symmetric and antisymmetric motions was developed. Leppington expressed the radiation efficiency of a rectangular panel as well as the vibroacoustic response under a reverberant field of thin orthotropic panels.

To deal with the wave characteristics in periodic structures, the Wave Finite Element Method (WFEM) is used. This spectral formulation is a result of a coupling between the conventional finite element method and the periodic structure theory. Its formulation starts with the discretization of the studies structure. An eigenvalue problem is then formulated using the periodicity of the structure. The general theory of the WFE is proposed by Mead and was improved by Zhong and Williams. This approach is then used for predicting the acoustic behavior of anisotropic plates. It investigates the evolution of radiation efficiency and sound transmission loss with frequency.

In all presented formulations, the input parameters are deterministic. However for layered structures, there is a high variability of mechanical parameters. The main novelty of this paper is investigating the effects of the uncertain mechanical parameters on the acoustic behaviour of anisotropic structures, especially in mid- and high frequencies.

This paper discusses the effect of uncertain parameters on vibro-acoustic behavior, especially on the Sound Transmission Loss (STL) of composite panels. The formulation presented is hybridization between spectral, energetic and uncertain methods. The Uncertain inputs parameters are represented using a parametric probabilistic approach which allows for the separation between the deterministic and the stochastic components in the process.

The second order stochastic parameters are developed using the generalized polynomial chaos expansion. In order to evaluate the outputs, there are two different methods: intrusive and non-intrusive methods. The efficiency of the approach is exhibited for isotropic and orthotropic panels.