Finite Element Simulation of Edge Absorbers for Room Acoustic Applications

To perform acoustic treatments in rooms for the low frequency range, porous absorbent material is often placed in or close to the edge of the room. This work presents a simulation procedure based on the Helmholtz equation which is solved using the Finite Element (FE) method. Thereby, the complex density and bulk modulus of the used porous material is obtained by fitting the Johnson-Champoux-Allard-Lafarge model to measurements in an impedance tube using the four-microphone method. The simulated room is modeled with sound-hard boundary conditions and has the same dimensions as the echoic chamber at the Building Physics Laboratory at Graz University of Technology. From the FE simulations, transfer functions are computed, which allow for a comparison to decay curve measurements following ISO 354 obtained in the echoic chamber. Therewith it can be shown that the simulation results are in good agreement to the measurements. The FE simulation results allow for a prediction of the sound field in the room, additionally the simulated sound field in the absorber can be visualized.