Currently, porous absorbers are used for the improvement of room acoustics. These may consist of different materials, such as:
- glass or mineral wool,
- natural or polyester fibers,
- open or closed-cell foams
- fiber reinforced plastics
The essential property of porous absorbers is a resistance to the incident sound wave, resulting in a damping effect. From a physical point of view, the damping results from the friction between air molecules and absorber skeleton. Hence, the acoustic absorption can be computed on the basis of a flow problem, where the flow resistance is determined by the solution of the Stokes equation for the complicated microstructure.
The computation of the acoustic properties The computation of the acoustic properties to completely new possibilities of material optimization. First, the measured microstructure is reconstructed by a stochastic model with the software package GeoDict (www.geodict.com), which has been developed at the ITWM. The complicated absorber structure can now be specifically varied on the computer, in order to study the influence of different parameters on the acoustic properties, such as fiber diameter, orientation, or compression.