The height of noise measurements matters

Historically, environmental noise measurements have been performed at heights of 1.2–1.5 m, until the European Union defined 4 m as the reference height for strategic noise maps. This has led to the question of whether measurements at one height or the other make a difference; the question arises because pedestrians’ exposure could be underestimated by sound pressure levels measured at 4 m above ground level. This paper presents an analysis of 243 simultaneous measurements at 1.5 m and 4 m above ground level, performed in five cities in Spain and Uruguay with different populations, in locations with distinct characteristics. The objective was to compare their signs and absolute values, and to determine whether they can be considered statistically comparable with a 95 % confidence level. For this purpose, statistical tests were performed. The results of the Wilcoxon pairwise differences test showed that 80 % of the series were not statistically comparable. In light of this fact, environmental sound pressure level measurements should be conducted at the height of interest, since the phenomena described by measurements at different heights don’t describe in the same way the same acoustic phenomena.