Improved noise map accuracy by using GPS acquired vehicle speeds: study of predicted equivalent noise levels using the Nord96 and Nord2000 models

Abstract

The noise maps in Sweden have always been constructed with the Nord 96 calculation model using the signposted speeds. This project investigates the limitations of this model, as well as what differences arise when the signposted speeds are exchanged for the real recorded vehicle speeds. In this case, the GPS acquired speeds were used. Different steps in the Nord 96 calculation model that could influence the changes in the noise maps were addressed, as well as the differences between the Nord 96 and Nord 2000 models. The influence of the percentage of heavy vehicles, different vehicles categories and importance of the acceleration of vehicles is investigated. The main goal of this paper was to investigate the possibility of creating a set of measures to be used as a correction for the current calculation model. This investigation is conducted on the subject area consisting of Kävlinge, Furulund, Löddeköpinge, and Björnstorp area. The Kävlinge area is closely investigated and the individual streets are analysed for the purpose of detecting the causes of sound pressure level differences on a small scale. Significant results were obtained, showing that difference in noise level can be up to ± 5 dB in some street segments, which is detectable by human ears. The correction of the current model is concluded not to be possible by just taking the average SPL difference for different street types and speed limits, thus the further investigation is needed.