Noise levels on the shielded side in cities using a flat city model

The prediction of road traffic noise levels in areas not directly exposed, such as areas behind buildings and courtyards, is difficult using standardised methods. This is mainly due to the fact that traditionally only one or a few sources are included. Here a simple model that assumes a flat city on rigid ground is used to demonstrate that sources from a large area are important. Calculations are compared to measurements for four cases, and the proposed method predicts levels 6-10 dB too high for the equivalent level at all measurement positions. If a correction is applied for this over-estimation, the results agree well.