Acoustic effects of a tree simulated by a FDTD model

Abstract

Trees and forests as a natural noise barrier would be an eco-friendly solution for noise reduction, as they have additional positive effect for air quality too. To quantify the sound attenuation by trees, the simulation of sound propagation in and around forest areas requires a detailed understanding of the acoustic properties of single trees. Therefore the acoustic effects of different trees are investigated by means of a three-dimensional finite difference time domain (FDTD) sound propagation model within a frequency range from 50 to 1500 Hz. The choice of the model type instantaneously enables the consideration of multiple reflection and diffraction. The influence of trunk size, branch density and the shape of the tree on backscattering and transmission is studied. The spatial resolution in this case is 5 cm. The acoustic properties of real and idealized trees are compared and presented to attain a classification for the typical tree parameters. As earlier studies have shown the main effect results from the diameter of the trunk. Another important parameter is the density of branches within a volume. This is described by the partial volume and the partial cross section. The long-term objective of this study is to gain a new parameterization for a realistic implementation of canopy in sound propagation models.