Assessment of the Influence of Seasonal Variation on Road Traffic Noise.

For road traffic noise assessments, long-term noise estimates are usually based on short-term site measurements. These short-term measurements are often based on a random sampling strategy, with measurement durations ranging from 15 minutes to a number of hours, depending on the method adopted and completed at the time of commissioning. Further, these measurements are often used as the basis to estimate long-term levels of a variety of indicators, including Lmax and Leq. In order to support the use of such a strategy, robust statistical methods should be used to validate associated assumptions. Using statistical assessment techniques previously applied by the authors to sites in Connecticut and California, this paper presents results of a statistical analysis of time history noise levels recorded at 14 different sites across Dublin City, Ireland. Measurements at each site were logged in five minute intervals over three years. At sites dominated by road traffic noise, measurements yield distinct seasonal variation and thus suggest that any extrapolation of short-term measurement data to yield long-term estimates should account for this variation. The paper will show how the seasonal variation can be included within predictive analysis to determine the sound level to be used in calculations.