Influence of stand characteristics on the acoustic forest floor effect

Forest floors contribute significantly to the noise abatement one might get from tree belts along surface transport infrastructure. However, little is known on what type of forest floor is most effective in maximizing the ground attenuation, and to what extent this is influenced by tree species. In addition, the spatial variability of the forest floor effect is of interest as well. In the current study, a two-microphone measurement setup was used to derive, by reverse engineering, the soil properties of concern for the interaction between the forest floor and sound waves. The Zwikker and Kosten phenomenological and slit-pore impedance model were considered and evaluated for their ability to reproduce the measured short-range spectral level differences (assuming rigid-backing). For both models, parameters were successfully derived for mono culture plots of ash, cherry, lime, maple, beech and oak.