Signal Processing and Speech Communication Laboratory
homephd theses › Modelling and simulation of porous absorbers in room edges

Modelling and simulation of porous absorbers in room edges

In work
Eric Kurz
Research Areas

Edge absorbers are known for their high effectiveness in absorbing low-frequency sound energy. Particular attention must be paid to low-frequency sound energy and especially low-frequency reverberation when planning and/or renovating communication rooms, as these have a sensitive effect on speech intelligibility due to masking effects. Here, edge absorbers, commonly known as bass traps, can be used as a subtle and relatively inexpensive acoustic treatment. Although the influence of edge absorbers on the sound field and its decay behaviour has been extensively proven empirically, no suitable modelling of the edge absorber exists to date. For this reason, edge absorbers are hardly ever used in room acoustic simulations.

This dissertation aims to find a computationally efficient calculation rule for predicting the influence of a porous absorber in room edges of a cuboid room on the stationary sound field and its decay behaviour in this very room. In this context, computationally efficient means that a calculation can be carried out with reasonable technical and temporal effort with sufficient precision. For this purpose, the validity of the Waterhouse theory shall first be checked by means of sound pressure and velocity measurements in room edges. In the course of the validity check, the concept of diffusivity will also be discussed, as this represents an essential basis of the Waterhouse theory. Since edge absorbers do not achieve their absorption efficiency exclusively via the Waterhouse effect, but to a large extent via the attenuation of the modal sound field, the next step will be to combine both ways of looking at the sound field. Based on this modelling of the sound field in room edges, an extension via a complex-valued wave number can lead to a model of the sound propagation in edge absorbers. The complex-valued extension can be done by using poroacoustic models. Thus, it should be possible to predict the influence of the edge absorber on the stationary sound field in a room. In a next step, it should be clarified whether the time constant of the decay process (reverberation time) of the sound field can be concluded from the reductions of sound pressure and sound velocity levels of the stationary sound field by introducing an edge absorber in a cuboid room. In order to verify the modelling for the edge absorber determined in this way, both measurements of the corresponding target variables and simulations with numerical calculation software are to be carried out.