Field measurement of ground effect for road traffic noises

In ASJ RTN-Model 2018, which was proposed by the Acoustical Society of Japan, a practical calculation method of the ground effect in A-weighted overall level for road traffic noise is specified by relatively simple formulae. The method is derived from the solution of the ground effect based on wave theory. By the practical calculation method, the attenuation level by the ground effect for a relatively long distance between the source and receivers tends to become larger on softer ground. Especially in the cases of lower sound source positions as specified in the ASJ RTN-Model 2018, the excess attenuation becomes large. To investigate the appropriate treatment of the ground condition in the case of road traffic noise propagation on soft ground, the authors have performed a field measurement of road traffic noise. The measurement results were compared with calculation results by both the ASJ RTN-Model 2018 and the theoretical solution based on the wave theory. From the comparison, the features of the propagation characteristics obtained by the ASJ RTN-Model 2018 were discussed.