In automotive industry, acoustic trim materials are widely used in order to reach passenger comfort targets. The dynamic behavior of the poro-elastic materials is typically modelled by the Biot theory, which however leads to expensive numerical finite element calculations.One way to deal with it is to use the Patch-Transfer-Function (PTF) sub-structuring method, which couples subdomains at their interfaces through impedance relations. This was done already for systems including locally reacting poro-elastic materials.In this paper, a methodology is presented allowing to numerically assess the PTF impedance matrices of non-locally reacting trim materials using the Biot based poro-elastic model solved by the finite element method (FEM). Simplifications of the trim impedance matrices are introduced resulting in considerable calculation cost reductions. The associated prediction errors are discussed by means of a numerical case study. The numerical test case consisted of a clamped plate covered with a double layer trim radiating into a rectangular air cavity. It is shown that a considerable calculation time reduction may be achieved while keeping prediction accuracy at an acceptable level.