Outdoor sound propagation: comparisons between calculations performed with atmos, a pe-based model, and wind tunnel experiments

Noise impact of road and railway infrastructures are more and more severely regulated by national laws: acceptable thresholds and reception levels are decreasing. It becomes necessary to predict more and more finely meteorology and its interactions with boundaries effects in current sound prediction models. ATMOS (Advanced Theoretical Models for Outdoor Sound propagation), a PE (Parabolic Equation) based calculation code dedicated to complex outdoor situations, has been developed to fulfil this need. In order to validate it, a measurement campaign has been performed in the wind tunnel of CSTB, Nantes (France). Such measurements present many advantages compared to outdoor experimentations. The main one is the possibility to control precisely many parameters such as temperature, wind speed profile and wind direction. Aerodynamic measurements as well as computational fluid dynamic simulations with FLUENT have also been undertaken in parallel to acoustical studies. Their results have been used to perform excess attenuation calculations with ATMOS. Comparisons between measurements and numerical simulations for realistic complex traffic noise configurations are presented here for a few cases (flat ground, impedance jump, noise barrier, embankment).