Road traffic noise reduction by vegetated low noise barriers in urban streets

Paper in proceeding, 2012

Low-height noise barriers were shown to significantly reduce road traffic noise since these can be placed very close to either source or receiver. In this study, it is investigated to what extent such devices can be used in a street canyon setup. Full-wave numerical calculations have been carried out with the FDTD (finite-difference time-domain) method, the PSTD (pseudo-spectral time-domain) method and BEM (boundary element method). In addition, a combined ray model and radiosity (CRR) model has been used. Numerical results of the different wave-based methods have been cross-validated with satisfying agreement. The limitations of an energy-based method like CRR have been pointed out. 4-lane road traffic in a 19.2-m wide street canyon with a realistic façade profile has been considered. In the predictions, low screens are considered, covered by vegetated wall substrate. Different arrangements of such screens have been assessed, for receivers on walkways and distributed over the building facades. Road traffic noise could be reduced on walkways at low vehicle speeds, even when both sources and receivers are located in the same reverberant space. Some shielding for higher elevated receivers along facades is predicted as well. Absorption on the low-height noise barriers was shown to be essential to obtain positive effects.