The importance of roof shape for road traffic noise shielding in the urban environment

The influence of roof shape on sound propagation in a densely build-up city centre is evaluated. Road traffic noise propagation from a street canyon to an adjacent, non-directly exposed building façade is numerically studied by the finite-difference time-domain method. A large number of common and less common roof shapes were analyzed in an idealized city canyon configuration. Roof shape can be responsible for differences in road traffic noise shielding exceeding 10 dBA, averaged over the shielded façade. Therefore, roof shape can be considered as an important means to limit sound pressure levels at a quiet side; various researchers indicated that the presence of silent zones and façades may limit city noise annoyance. With increasing vehicle speed, the choice of roof shape becomes more important. The roof top height was shown to be a bad predictor of shielding efficiency in the equal-building-volume approach followed in this study.