Prediction of the attenuation of road traffic noise with distance

Abstract A method is described of calculating the sound pressure level received from single, representative light and heavy vehicles after propagation over terrain composed of various combinations of hard ground and grass-land. These results are then used to derive correction contours for the attenuation with distance of the Leq level received from streams of each class of vehicle. The results apply to conditions where the boundary between the soft and hard areas is parallel to the traffic stream and the soft ground is on the receiver side. Various positions of the boundary are considered. A simple prediction method for Leq is developed, incorporating the distance corrections. Similar calculations are carried out for the attenuation with distance of the L10 noise index for a representative stream of vehicles. Based on these results simple prediction equations for the excess attenuation are proposed in terms of the receiver position and the proportion of soft ground below the propagation path.