Trim FEM Simulation of a Headliner Cut Out Module with Structureborne and Airborne Excitations 2012-01-1524
Due to increasing attention paid to the optimization of leakages and passthroughs in general, measurements on cut out modules in large coupled reverberant rooms are often carried out in the middle and high frequency range, in order to optimize the insulation performance of trims installed in their actual environment (Transmission Loss). Using optimal controlled mounting conditions, we have been able to extend the frequency range to the low frequencies in order to validate trim FEM models of a headliner cut out module with structureborne and airborne excitations.
Both coupled response with movable concrete cavities (structureborne excitation) and Transmission Loss with coupled reverberant rooms (airborne excitation), or pure acoustic response with a monopole source positioned in the movable concrete cavity (airborne excitation in order to quantify absorption effects), have been measured and simulated using poroelastic finite elements for various types of trims on the same setup, without any change on the mounting conditions. An additional movable absorbing environment in the large reception room has been deployed in order to carry out laser vibrometer (skeleton velocity) and p-u probes (particle velocity and intensity) measurements on the surface of the headliner trim.
By incorporating the maximal treatment mock-ups of the cut out modules as additional trims in the models, we have obtained good correlation results between measurements and simulations for both bare and trimmed configurations in the low and middle frequency range up to 600 Hz with structureborne excitation and up to 1000 Hz with airborne excitation, while maintaining reasonable computational times, due to the reduced size of the problem.