Traffic noise in shielded urban areas: comparison of experimental data with model results

Noise maps of cities are commonly produced with rather simple engineering models for sound propagation. These models may be inaccurate in complex urban situations, in particular in situations with street canyons. Street canyons are urban areas that are partly or completely enclosed by buildings, for example a street between two buildings or a backyard surrounded by buildings. In this paper we study sound propagation from a city bus in a street canyon to a receiver in a nearby street canyon. Multiple reflections of sound waves in both the source canyon and the receiver canyon play an important role in the sound propagation. Experimental data are compared with three types of model results: i) results of a numerical boundary element model, ii) results of a 1:30 scale model experiment in a semi-anechoic room, and iii) results of the Dutch standard engineering model, which is similar to the international standard ISO 9613-2. The data are in reasonable agreement with model results i) and ii), while the engineering model yields sound levels that are about 6 dB too low. Keywords: urban noise, street canyons, sound propagation, noise measurements and prediction, numerical models, scale modelling, engineering model