Traffic Noise Attenuation as a Function of Ground and Vegetation. (Final Report)

摘要

This final report presents the results of measured excess attenuation rates fortraffic noise propagating over acoustically absorptive terrain in terms of the alpha site parameter, as used in the FHWA Highway Traffic Noise Prediction Model (FHWA-RD-77-108). The study was part of a federally-funded research project that focussed on two noise propagation phenomena: (1) excess attenuation provided by various ground covers; (2) shielding by shrubs and trees typically used in landscaping along freeways. Results of the latter were published in a 1989 interim report (FHWA/CA/TL-89/09) by the same title and author. A summary is repeated in this report. Noise levels of single vehicle passbys were measured at distances from 7.5 to 122 m (25 to 400 ft), and at heights from 0.8 to 6 m (2.5 to 20 ft) above the ground. A total of 541 measurements were made using up to ten microphones simultaneously at four acoustically absorptive (soft) sites. Additional verification measurements were made at four-lane highway sites. Meteorological parameters were mwesured simultaneously with the noise. Excess attenuation rates in terms of alpha were calculated from the data.