Double walls are increasingly used in construction. Due to this, there is interest in reliable models of their sound insulation for the frequency range reguired in regulations (50-5000Hz). These models can be either statistical or deterministic. In this work, the finite layer method (FLM) is presented as a numerical technique for solving the problem in a deterministic way. it is used for discretising the Helmholtz equation in the cavity and combines a finite element method (FEM) discretisation in the direction perpendicular to the wall with trigonometric functions in the two in plane directions. The FLM exploits the simple geometry of the double wall and accounts for all its boundary and interface conditions with a reasonable computational cost. The statistical energy analysis (SEA) is a more suitable framework of analysis for vibroacoustic problems in large domains such as buildings. However, the best SEA approach for modelling double walls is not clear in the literature. The cavity is considered as a subsystem or treated as a connecting device between the two leaves depending on the autor. The finite layer method is a used to evaluate the performance of these two approaches, concluding that both considerations have to be taken into account together to reproduce the real behaviour. Finally, the FLM is used to define a combined deterministic energy based approach to deal with this kind of problems.Peer ReviewedPostprint (published version
