Improving the soundscape quality of urban areas exposed to aircraft noise by adding moving water and vegetation

Research shows that the sight of trees and the sound of moving water improve the soundscape quality of outdoor spaces exposed to road traffic noise. Effects are attributed to non-energetic masking, visual attentional distortion, and congruence between sight and hearing. However, there is no literature on such effects for aircraft noise. Aircraft noise varies from other traffic sources, i.e., in terms temporal variability, duration, and spectral composition, complicating the application of findings without further research. In a virtual reality experiment reported in this article, participants were asked to rate scenarios with different sound levels of flyovers, urban typologies, vegetation, and/ or water features. The results showed a significant improvement of the soundscape quality when (1) vegetation and (2) moving water were present, and especially when (3) vegetation and moving water were presented simultaneously, especially for residential areas in terms of the relative change. Moving water also reduced the saliency of aircraft flyovers significantly, changing the constellation of fore- and background sounds. Moving water raised the perceived audibility of the most dominant sound source too, which could be attributed to non-energetic masking effects. The findings of this study indicate that soundscape strategies can complement noise abatement in areas prone to aircraft noise.