THE ESSENTIAL
- Swedish residents healthier following switch to quiet electric buses
- Noise pollution impacts people’s physical and mental health
A reduction in fatigue, daytime sleepiness and bad mood: these are the positive impacts of the introduction of fully autonomous buses on line 60 in Gothenburg, Sweden in autumn 2019.
These improvements are due to the level of noise suffered by the inhabitants, which has been greatly reduced thanks to the switch to electric. The sound levels of the old bus transport system had been perceived as annoying, especially on the climbs, because they were low frequency noises.
“Thumbs”
However, these noises, also called “deaf noises”, because we hear them even if we cover our ears, are particularly harmful. Indeed, they have a high potential for disturbance because they are less well attenuated by facades or noise barriers. In addition, the perception of low frequencies is different from that of other frequencies: at low sound levels, they are not perceived, but as soon as they become audible, the sensation of sound volume increases more quickly than for other frequencies.
In homes, the noise pollution linked to low-frequency noise is, for example, the vibrations generated by the lift or the heating, the noise of children running, the sound of footsteps or even the sounds coming from a “home cinema” .
“We can be disturbed by different noises, but the problem with low frequency noise is that it is less well attenuated by facades or windows and therefore enters homes more easily. Even small increases in its level are perceived as very noticeable“, explains Kerstin Persson Waye, professor of environmental medicine at the Sahlgrenska Academy of the University of Gothenburg, who directs the “Sound environment and health” group at the origin of the research.
Noise measurements
The study consisted of questionnaire surveys of randomly selected residents in two phases, before and following the switch to electric buses. Half of the inhabitants lived in houses located along the bus line in two areas of the city: Masthugget and Lunden. The other half, who lived some distance away, constituted the reference group.
According to this study, regarding changes in noise levels, the proportion of respondents who noticed noise from buses fell from 75% to 39%, and the proportion of people who were very annoyed by noise fell from 26% to 5%.
At the same time, noise measurements were taken in several houses, including indoors. These exceptional measurements required a special setup with 10 to 12 microphones in each housing to provide correct and representative low frequency noise data.
Influencing public health
A marked decrease in perceived health effects was observed: the proportion of people feeling exhausted once or twice a week fell from 49% to 39%, the same proportion as in the reference group. The proportion of people in a bad mood dropped from 22% to 17%, and far fewer people reported being very sleepy during the day.
“So there was an improvement: people felt significantly better. Although we cannot say with certainty that the results reflect the entire population and that the positive health changes are long-lasting, we believe that they can be generalized in residential settings where bus transport represents a large part of the exhibition. Also, as other forms of transport in the urban environment become quieter, this might influence public health.“, concludes Kerstin Persson Waye.
In France, noise is a very present nuisance in daily life: 86% of French people say they are bothered by noise at home, according to the Ministry of Health. Beyond the annoyance, excess noise has effects on health, auditory (deafness, tinnitus…) and extra-auditory (cardiovascular pathologies…).