Attenuation of highway noise by narrow forest belts

Abstract

Over the last several years highway noise prediction methods have been refined and calibrated for sound propagation over open terrain and interacting with complex physical barriers. However, very little work has been done in the area of traffic noise propagation through bands of vegetation, which most laymen feel offer the most feasible means of reducing traffic din. The lack of research in this area is probably due to the general feeling shared by most acousticians that narrow bands of vegetation adjacent to highways provide little physical noise reduction. This paper briefly describes current highway noise prediction methods as related to vegetative barriers and presents results from a comprehensive study of sound attenuation by narrow forest belts recently conducted at the Pennsylvania State University. Based on extensive field measurements, values of insertion loss are reported for point source, as well as for quasiline source conditions. These results are compared with models currently approved for use in predicting highway noise. In closing conclusions based on data collected are presented along with recommendations for future work in this area. [Work supported by the USDA Forest Service, Northeastern Forest Experiment Station through the Pinchot Institute for Environmental Forestry Research and the Federal Highway Administration.]