Modeling road traffic noise using distributions for vehicle sound power level

Research evidence suggests that annoyance, sleep disturbance and other health effects of road traffic noise exposure may be related to the level and number of noise events caused by traffic as well as to energy equivalent measures of exposure. Because measurements show that the variation in noise emission between vehicles within the same category can be considerable, it is essential that the influence of vehicles that are producing significantly more (or less) noise than the average vehicle are taken into account in order to correctly predict the occurrence and strength of road traffic noise events (and in particular to calculate indicators that characterize these noise events). However, current state-of-the-art instantaneous vehicle noise emission models usually only consider a single emission law for each vehicle class. In this paper, an approach for predicting instantaneous sound levels caused by road traffic is presented, which takes into account a measured distribution of sound power levels produced by individual vehicles, for each vehicle category. The effect of this approach on estimated energy equivalent levels, percentile levels and sound event indicators is investigated for the simplified setting of a receiver along a dual-lane road carrying free flow traffic.