An efficient model for background noise mapping
Paper i proceeding, 2012
It has been shown that inhabitants of dwellings exposed to high noise levels benefit from having access to a quiet side. Therefore the European Environmental Noise Directive allows member states to include the presence of a quiet side in their reports. However, current practice applications of noise mapping methods usually underestimate the noise level at the shielded façade when the most important contribution is sound propagation over the rooftop. Multiple reflections from opposite façades in street canyons are not sufficiently taken into account. In addition, sources at distance much larger than normally taken into account in noise maps might in some cases still contribute significantly. Since one of the main reasons for this poor approximation is computational burden, an efficient engineering model is proposed, which considers multiple reflections and turbulence scattering. The model uses an analytical function of a complexity comparable to ISO 9613 formula for noise barriers that is fitted to an extensive set of FDTD (finite difference time domain) simulations of canyon-to-canyon sound propagation. This model allows calculating the background noise in the shielded areas of a city, which could then be used to refine noise mapping calculations.