Research On The Characteristic And Methods Of The Highway Noise Reduction By Afforestation

There appears to be a widespread popular belief that tall hedges and narrow belts of trees cause a significant reduction in traffic noise. Voice assessment methods of highway have been extensively studied. Those survey respondents residing close to the road indicated that the vegetation had given the better noise reduction; however, the Road traffic noise attenuation by belts of trees is rarely studied in China. As the noise pollution is severe now, the methods of highway noise barriers, walls, banks and tree belts are more and more important to reduce the noise. We then choose a more effective and economic way such as noise reduction tree belts, in order to propagate this method.Fisrt of all, in order to find the behavior of the noise attenuation through the tree belt designed for noise reduction, we put a survey in practice in highway. The effects of noise reduction of six tree belts were examined. Net noise reduction effect termed as"additional attenuation"was obtained by subtracting the sound pressure level at each measurement site behind the tree belt from the sound pressure level at equal distances over open ground. This investigate covers the terrain of the site, the figure and the shape of the trees, the variety of the trees. The noise and afforestation around JING-SHI and JING-JIN-TANG expressway are compared. The conditions of the site are considered according to the result of the survey. The relationship between the formation, density and height of many kinds of tree belts, plantation wall and the noise reduction performance are also taken into consideration.Secondly, on the basis of the survey data, the attenuation model is founded. The relationship of five parameters were studied, including Architecture of trees, height and width of the tree belt, height of noise source, and the distance between noise source and receiver. The order of importance of the five parameters in relation to additional attenuation was developed. The optimized width of the tree belt is calculated according the curve of the noise attenuation.Finally, based on this research, the example of design and practice of highway noise"green barriers"are needed. Some issues and advises that must be noticed in designing and building of the noise reduction afforestation are put forward. According to the site landscape, the seed and formation of the trees in JING-SHI expressway are redesigned to exert the function of noise reduction.