A segment-based A-weighted sound propagation model for road traffic noise assessment: A general concept

The propagation model of the road traffic noise established by the Acoustical Society of Japan, the ASJ-RTN Model 2018, directly obtains the A-weighted sound pressure level by assuming specific power spectra of vehicle sources in a single calculation. This is more effective in reducing computational burden than European models, which typically require calculations in eight bands from 63 Hz to 8 kHz. However, the ASJ model has not been generalized enough to deal with an arbitrary terrain profile, contrary to the European models where the handling of a segmented terrain profile is integrated. This will become a major obstacle in realizing noise mapping in Japan. In this paper, a concept of an A-weighted sound propagation model for road traffic noise with integrated handling of a segmented terrain profile is presented. The model combines the segmented modeling of multiple diffractions over a complex profile and the Fresnel weighting of ground characteristics both employed by Harmonoise, the mean plane for ground modeling used in CNOSSOS-EU, and the calculation of the excess attenuation terms following the ASJ model. Preliminary calculation results show that the model agrees reasonably well with finite-difference time-domain simulation results on flat and uniform ground, but still needs investigation for non-flat and nonuniform ground.