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Sounds alarming
17 March 2001
From New Scientist Print Edition.
Duncan Graham-Rowe

Children can be stressed out by everyday noise at levels too low to damage their hearing, according to research in the US and Austria. Chronic exposure to nearby sounds such as roads and train lines could also create problems with motivation.

The study, commissioned by the Austrian Ministry of Health, found that children living in relatively noisy neighbourhoods had raised blood pressure, heart rates and levels of stress hormones. "Non-auditory effects of noise appear to occur at levels far below those required to damage hearing," says Peter Lercher of the Institute of Social Medicine at the University of Innsbruck, Sonnenburgstrasse, who carried out the study with Gary Evans from Cornell University in Ithaca, New York.

"We are really not looking at loud kinds of noise. They are typical levels found throughout neighbourhoods in Europe," says Evans. "It suggests that children living in noisier areas of residential communities are subject to stress."

We don't know much about the non-auditory health effects of exposure to everyday noise at lower intensity, says Evans. Previous research has focused on what happens to hearing when people live near excessively loud noise from airports or high-speed rail lines, for example. This is the first study to examine the stressful effects of low-intensity noise.

Evans and Lercher took 115 nine and ten-year-olds from alpine villages in the Inn Valley region of Tyrol in Austria and divided them into two groups: those living in neighbourhoods with noise levels of less than 50 decibels and those with levels higher than 60 decibels. They tested each child's blood pressure, heart rate, and cortisol and adrenalin levels while they were resting.

Background noise had a significant effect on stress levels, says Lercher. The researchers want to know how this affects children's health in the long term. "Anything that increases blood pressure over time is something to worry about," says Evans.

Questionnaires and motivation tasks also revealed that this kind of stress could weaken a child's motivation. Prolonged exposure to noise that children have no control over appears to lead to "learned helplessness" syndrome, the researchers report. The same condition has previously been linked to forms of depression and to poverty. "It's a pretty pervasive phenomenon," says Evans. "Girls in particular seem to be a little bit more vulnerable to learned helplessness."

According to John Stewart, chairman of the UK Noise Association in London, the research confirms anecdotal evidence from people living under flight paths that prolonged exposure to noise levels within safety limits can still be bad for your health. This is precisely the kind of issue that governments have failed to acknowledge for years, he says. "What they really refuse to look at are lower levels of noise that is fairly constant," says Stewart.

From issue 2282 of New Scientist magazine, 17 March 2001, page 5

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