Effect of ground between double barriers on road traffic noise propagation: Investigation through three-dimensional wave-based numerical analysis

The ASJ RTN-Model, a road traffic noise prediction model proposed by the Acoustical Society of Japan, presents a method for calculating noise propagation with double diffraction around parallel noise barriers, but it does not take into account the effects of reflections from the ground surface between the barriers. In this study, we conduct three-dimensional wave-based numerical analysis to investigate the effect of the presence or absence of the ground surface between the barriers on the propagation of road traffic noise, varying the heights of source and ground surface. The results show that, although the effect of the ground surface is generally small when considering road traffic noise, the presence of the ground surface increases the sound pressure levels in the receiver region. Furthermore, we propose a simplified calculation model to include the ground surface influence in the ASJ RTN-Model and evaluate its effectiveness. The evaluated results also show that the proposed calculation model reduces the discrepancy between the ASJ RTN-Model and wave-based numerical analysis results compared to direct application of the ASJ RTN-Model.