Linking ISO Dynamic Stiffness and Acoustic Modal Identification for FEM-Oriented Modelling of Elasticized Expanded Polystyrene

Elasticized expanded polystyrene (EPS-T) is widely used as a resilient layer in floating floors, where dynamic stiffness is the key input for impact-sound prediction, while FEM modelling additionally requires elastic parameters and damping descriptions consistent with the adopted test or modelling configuration. This study investigates whether ISO-type dynamic stiffness testing and acoustic-response modal identification can provide consistent vibroacoustic parameters for EPS-T. Rectangular specimens of different thicknesses were tested for dynamic stiffness and damping using an ISO 9052-1-type setup. Additional cylindrical compression tests were used to examine apparent Young’s modulus and Poisson’s ratio, while impulse-excited acoustic responses of clamped specimens were combined with inverse FEM identification. The ISO-type dynamic stiffness decreased from approximately 53.3 MN/m3 for nominal 17 mm specimens to 27.0 MN/m3 for nominal 53 mm specimens. This trend was described by a compliance model with an effective Young’s modulus of 2.04 MPa and an equivalent contact/support stiffness of 101.2 MN/m3. Acoustic-response inverse FEM gave consistent Young’s modulus values, ranging from 1.77 MPa to 2.16 MPa, with a mean close to 2.05 MPa. Direct use of s′ = E/h overestimated stiffness and underestimated predicted ΔLw by approximately 2–5 dB. The two routes provided consistent estimates of the effective modulus, but this consistency applies only to modulus identification and not to direct stiffness conversion or damping transfer.