Double-wall systems are widely used in several applications such as building, automotive and aeronautics thanks to their acoustic and thermal insulation performance superior to that of single walls. The introduction of an interlayers of porous materials between the panels significantly improves the acoustic reduction index of the system. Depending on the frequency band of interest, several numerical approaches can be used. The finite element method [1] is widely used for the low-frequency range in order to capture the influence of various geometric, mechanical and acoustic parameters of the problem and to study the dependence between the eigenmodes of the system and its frequency response. For medium and high frequency domains, this method becomes very computationally expensive and approaches such as the Transfer Matrix Method (TMM) or the Statistical Energy Method (SEA) are more suitable [2]. The first part of this work is devoted to the sound transmission prediction of double-walled structure with porous layers subjected to a diffuse acoustic field using the TMM method. The principle of this method is the representation of the plane waves propagation in the different layers in terms of transfer matrix. The numerical optimization of the acoustic insulation properties of such system requires knowledge of the most influential parameters in order to reduce the computational cost. Global Sensitivity Analysis (GSA) methods can be used for this end. In the second part of this work, the GSA Morris method is used to ascertain the non-influential parameters of the model [3 ,4]. This technique consists of a OAT (One-At-a-Time) design of experiments with a randomized direction of variation to estimate the elementary effects for each input parameter and to calculate the sensitivity indices. Finally, the results obtained by the Morris method based on the elementary effects are compared to the Sobol indices based on the variance.