Noise variability due to traffic spatial distribution

The inverse relation of the uncertainty of the equivalent sound pressure level to the square root of the number of vehicle pass-bys is investigated. The influence of the traffic spatial distribution is evaluated by means of a computer model, based on Monte Carlo and the Weyl–Ingard Theory. The model results are discussed and compared with experimental data. By least mean squares fitting of simulated results, a new expression is obtained for the sound pressure level uncertainty, that takes into account the receiver position, road configuration and traffic flow balance. This expression explains the different values found in the literature and yields uncertainty values that may not be covered by the ISO 1996-2:2007 recommendation, in some specific circumstances. Finally the path for building traffic noise uncertainty maps is sketched out.