Statistics of A-weighted road traffic noise levels in shielded urban areas

In the context of community noise and its negative effects, the noise descriptors used are usually long-term equivalent levels and, sometimes, maximum levels. An improved description could be achieved by including the time variations of the noise. Here, the time variations of A-weighted road traffic noise levels have been studied. Of special interest are situations with a shielded courtyard. For numerical results, a ray model has been used for calculating the sound propagation, and the traffic has been modelled as a Poisson process. With this model the statistics of A-weighted levels have been investigated for different situations with varying traffic flows. Results from an in-situ measurement have been compared with those from the numerical model, showing acceptable agreement. It is shown both by numerical modelling and measurements that the time variations in noise level are smaller in a courtyard than in a corresponding directly exposed situation. One of the additional conclusions is that the noise reduction of the maximum level can be significantly higher than that of the equivalent level