Relevance of Buildings in Aircraft Noise Predictions

It is common practice for ground-borne noise sources such as roads or railway lines to perform propagation calculations under consideration of buildings. As a consequence of the elevated source positions barrier effects as well as reflections are typically of minor importance for aircraft noise. Nevertheless they can locally influence the resulting sound exposure level as well as the characteristics of a fly-over event. In this exemplary study, the influence of buildings is studied for a region in Zurich, Switzerland. To that purpose, three different aircraft departures from Zurich airport are simulated with the recently developed aircraft noise model sonAIR including barrier effects as well as reflections. Our results suggest that buildings have a minor effect in case of direct fly-overs. However this is not the case for situations with grazing sound incidence. In such situations, barrier effects can lead to a substantial reduction of sound exposure levels. Reflections on the other hand cause relevant amplifications, however primarily at already shielded receiver positions. In total, buildings lead to lower sound exposure level. Therefore, at least for noise mapping purposes, the general practice to calculate aircraft noise without taking buildings into account, is supported.