In the present thesis a hybrid theory [Shorter and Langley 2005] for calculation of Coupling Loss Factors (CLFs) in hybrid Finite Element Method (FEM) / Statistical Energy Analysis (SEA) modelling is applied to a hybrid line junction, with the aim of providing a derivation example. The case study is chosen to be a hybrid line junction composed by a rigid beam modelled with FEM, which couples two incident SEA plates coincident to the beam along one of their edges. The theory allows to obtain the Coupling Loss Factors from the Stiffness Matrix of the deterministic subsystems and the Direct Field Dynamic Stiffness Matrix of the statistical subsystems.