A forestry influence on an acoustical perturbance propagation

Our goal was to study the processes of acoustical perturbations attenuation in the presence of forestry. Results of computational simulations of perturbations propagation through forest canopy based on the complete Euler?s equations set for the two dimensional case are shown in this paper. The approach had been already used by author in his simulations of the propagation of the non-linear acoustical impulse through vegetation. The influence of vegetation is represented with the mass-force of resistance taken into the account in the volume occupied with a forest. The examined type of noise is approximated with simple harmonical cylindrical waves. The numerical resolving of the equations set was performed using Godunov?s method. Technologies of the parallel computing used in the software implementation allowed avoiding difficulties caused by the importance of high-frequency components of the road noise being approximated. The described approach was used to perform simulations for various types of vegetation, distance between a source and a forest belt, its width, different frequencies and amplitudes of a disturbance. The influence of the near surface wind on the noise propagation through a stand of trees was also studied. Obtained results were analyzed and compared with the known experimental results. As a result of our modeling it was found that the patterns of canopy-noise interaction are mostly similar for different types of vegetation. The picture of interaction was influenced mostly by the absence or presence of the near surface wind. In the case when there was no wind the investigated model of the forest canopy showed almost no influence on the disturbance propagation. In the case of wind presence upward and downward fluxes arose on the near and far edges of the forest belt thus seriously increasing disturbance attenuation inside the forestry.