Predicting the Sound Transmission Loss of porous structures via poro elastic homogenization

by C. Moser - Montanuniversität Leoben

This project’s motivation is to increase passenger comfort by reducing the noise level inside an airplane. In recent airplanes there is a foam layer added to cabin interior panels which lowers the acoustic transmission from surrounding noise (e.g., the turbines). Therefore, the acoustic transmission of foams is studied – more specifically the effect of a foam’s micro-structure on the sound transmission behaviour. In open-pore media, the airflow through the structure determines the Sound Transmission Loss (STL). The STL describes the ratio of the pressure of the incident wave and the pressure of the transmitted wave. To represent foams, micro-structures based on “Kelvin” cells are modelled and airflow simulations are executed on those unit cells. The results of the airflow simulation are input parameters to use a homogenized poro-elastic material model in FE-simulation for the component scale structure to efficiently predict the STL over frequency. To validate this computational prediction, three variations of specimens were manufactured via 3D-printing to be tested using the standardized impedance tube experiment. The results of the prediction via homogenization and FE-simulation are then compared against the test results.