Fluctuating traffic noise levels calculated from time-dependent traffic data: an engineering approach

Temporal variations of traffic noise levels originate from two effects: (1) traffic variations and (2) atmospheric variations. Traffic variations include variations of traffic volume and vehicle speed, and cause variations of the emission of sound at the source. Atmospheric variations cause variations of the propagation of sound from the source to the receiver. In this article an engineering method is presented for the calculation of temporal variations of traffic noise levels, based on time-dependent data for traffic volume and speed. The method may be combined with engineering models such as the Dutch traffic noise model, the model ISO 9613-2, or the recently developed model Cnossos-EU. The method employs a simple formula for the timedependent effect of atmospheric wind and temperature gradients on sound propagation. The formula is derived from sound propagation calculations for a wide range of atmospheric conditions, performed with the Harmonoise model for traffic noise calculations. The engineering method developed in this article is used for a comparison with measurements near a highway in the Netherlands. Using time-dependent open traffic data for the highway, good agreement is obtained with sound levels recorded over a period of 24 hours. The method is of interest for urban traffic optimizations with environmental constraints, for example by means of â–œcity dashboards,â–? showing real time representations of traffic flow and traffic noise in a city.