Effective wavenumbers for sound scattering by trunks, branches, and the canopy in a forest

Sound propagation in a forest is often represented as propagation in free space with an effective complex wavenumber, which accounts for scattering and absorption. In this paper, the effective wavenumbers due to sound scattering by trunks, large branches, and the canopy are determined and analyzed based on three-dimensional multiple scattering theory. Trunks and branches are modeled as vertical and slanted finite cylinders, while the canopy is modeled by diffuse scatterers. The results are compared with two-dimensional effective wavenumbers previously used in the literature, which were obtained by approximating the trunk layer as infinite vertical cylinders.