摘要：In order to determine the effects of tree branches, leaves and their canopies on noise pollution, different types of trees from the Chitgar forest park in Tehran were investigated and compared in the seasons of spring and fall. Noise values were taken with noise meter equipment at four points of measurement: (a) an open area as the control treatment (without trees), urban forests of pure stands of (b) Pinus eldarica, Robinia pseudoacasia, and (c) a mixed stand at 7 distances (10, 20, 30, 40, 50, 75 and 100 meters from the source of the noise which was located behind the tree stands). The experiment was repeated five times in the above mentioned seasons. The noise pollution of the region was also taken into account. The results indicated that in the studied area, the average noise level was more than the Iranian national noise standard. The largest noise reduction occurred in the mixed stand, which was about 19.07 dB(A) and the lowest amount of reduction was seen in the pure stand of Robinia pseudoacasia which was about 14.7 dB(A). The most significant noise reduction took place 75 meters away from the source of the noise. The differences between noise pollution abatement of the pure stand of Robinia pseudoacasia and the mixed stand in spring and fall were 5.01 and 6.05 dB(A), respectively. The results of this study suggest that in order to solve the issue of noise pollution of industries and road traffic, especially in big cities like Tehran, noise barriers need to be specified in city construction in specific zones that are covered with trees and vegetation with appropriate width.
关键词：Noise pollution; mixed stand; fall season; Chitgar forest park; pure stand
