Parks, meadows and other urban green spaces are not only gaining in importance for the climate. Thanks to them, city dwellers also perceive the stressful road and rail noise in the settlement area as less stressful, as a study has shown. However, the green spaces apparently do not distract from the noise pollution from aircraft – on the contrary: the greener the environment, the more annoying the respondents found the aircraft noise.
On the way to work, in the office and in the apartment in the city center – we hear noise all the time. Traffic noise from cars, trucks, trains or planes is a particular burden for the many residents of urban areas. According to the World Health Organization (WHO), one in three feels annoyed by noise during the day, while one in five sleeps at night. The background noise has an influence on our health that should not be underestimated: Increased noise exposure can lead to stress, sleep disorders or even cardiovascular diseases and diabetes.
Green spaces reduce noise pollution from cars and trains?
Researchers led by Beat Schäffer from the Eidgenössische Materialprüfungs- und Forschungsanstalt (Empa) have now investigated how these negative effects of noise pollution can be reduced in densely populated, urban regions. In particular, they wanted to find out whether green recreational areas can reduce the subjective perception of noise from road, rail and aircraft noise. For this purpose, the scientists used the so-called “Normalized Difference Vegetation Index” (NDVI), which indicates the plant cover on the basis of infrared satellite data. They combined this data with green space information from the Swiss Federal Office for Topography.
In order to test the effect of parks, forests, etc. on the noise perception of residents of urban regions, the team compared this data with the results of the SIRENE survey. This study asked around 5,600 participants about noise pollution from road, rail and aircraft noise. The result: As already shown in other studies, most of the respondents felt subjectively less annoyed by road and train noise in a green environment. Whether a nearby park, a pond or mountains on the horizon – a look and walk into the green could significantly reduce the perception of noise. The closer the recreation zone was to one’s own place of residence, the lower the subjectively perceived annoyance from noise emissions. In the case of heavily greened areas, the perceived noise level was reduced by around six decibels for road noise and three decibels for rail noise.
Aircraft noise appears louder in the green
Interesting, however: the perceived noise pollution from aircraft did not reduce green areas for the majority of the respondents. Instead, most of them felt more disturbed by aircraft noise, the more green spaces they surrounded and felt the noise up to ten decibels louder. According to the researchers, this has different reasons. “While we can escape road or train noise by a little more distance, we cannot do that with aircraft noise,” explains Schäffer. According to the research team, we are at the mercy of the noise from the air, as we cannot escape it from a few meters away. This “being at the mercy” may lead to us perceiving this noise as more annoying.
So-called incongruence also plays a role: “We expect a park to be quiet. If this calm is then disturbed by something that we cannot influence, then we perceive this noise as much more distressing, ”says Schäffer. In contrast to the park or forest, we hardly notice an airplane in the sky in the big city and the aircraft noise is apparently more likely to go down. In order to research the results on noise perception in more detail, Schäffer and his colleagues want to further examine the psychological and physiological aspects of noise and include additional factors such as vegetation density. The aim is to also take these findings into account in future urban planning for heavily populated urban areas.
Source: Swiss Federal Materials Testing and Research Institute, specialist article: Environment International, doi: 10.1016 / j.envint.2020.105885