Outdoor Sound Propagation Models to Reproduce Low-Frequency Adverse Wind Effect on Road Traffic Noise Propagation

Wind is known to affect sound propagation outdoors. The effect becomes significant under a propagation distance of more than several tens of meters and makes impact on propagation of environmental noise in urban scale. Among such noise, road traffic noise (RTN) is a primary noise source in most urban situations. Hence, prediction of the wind effects to the RTN propagation is important. In this paper, measurements of the wind effects to the RTN propagation are performed. Furthermore, calculations using empirical and theoretical models are compared with the measurement results. For measurements, an anemometer and receiving points are placed along a line perpendicular to an embanked road with intense traffic with distances of 50 - 250 m from the road. Calculations simulating the measurements are performed using the Harmonoise engineering model, a theoretical model (Rasmussen, J. Sound Vib. 104, 321-335, 1986) and its modified models. The measurement results show decrease of excess attenuation with the increase of vector wind at middle and high frequencies, which is in line with known behavior. However, an adverse trend is seen in a low frequency. A modified Rasmussen's model was able to reproduce the adverse wind effects, whereas other models were not.