A comparison of two numerical models for outdoor sound propagation

Two established models for predicting environmental noise levels, the European ’Harmonoise’ and the Scandinavian ’Nord2000’, have been compared for a number of test cases involving a variety of source and receiver configurations, terrain profiles, noise barriers, properties of the ground, and meteorological conditions. The predictions are compared with reference data from the literature and from measurements conducted as a part of this project. In most cases the models agree very well, but in some cases the predictions deviate significantly from each other. There are many similarities between the approximations used in the two models, but some parts of the modelling methods are clearly different. The most significant differences between the two modelling methods are pointed out, and it is attempted to explain the observed differences between their predictions. Acoustic Technology Orsted•DTU July 24, 2007 i