Noise scattering and shielding by roadside trees: results from a scale model

Trees with randomized features of tree crowns, branches, and trunks produce various acoustical effects on the sound field and the noise propagation in urban areas. Acoustic measurements with 1:10 scaled trees were conducted to characterize the scattering and shielding effects on the pedestrian level and elevated locations. Properties of the tree models were altered to compare different configurations of trees: tree crown size, density of the foliage, and the gap between the array of trees. Scattered sound were captured below the tree crown and the decrement of sound pressure level behind the tree crown. Impulse responses and the sound pressure levels were analyzed, and the results showed that the noise levels in higher frequency bands were slightly increased at the pedestrian level. From the results of changes in the tree crown size and the density of foliage, the seasonal effects of trees on the acoustic environment can be discussed.