Details of the Noise and Children Study
Evans and his European colleagues analysed data on 115 fourth‑graders in Austria. Half the children lived in quiet areas – below 50 decibels (dB), the sound level of a cloth-es dryer or a quiet office. Half lived in a noisier residential area – above 60 dB, about the intensity of an average dish-washer or raised voices.
"We are really not looking at loud kinds of noise. They are typical levels found throughout neighbourhoods in Europe," says Evans. The non‑auditory effects of noise, however, appear to occur at levels far below those required to dam-age hearing.
The children in noisier neighbourhoods experienced higher overnight levels of the stress hormone cortisol, marginally higher resting systolic blood pressure, and greater heart rate reactivity to a stress test – all signs of modestly ele-vated physiological stress. Background noise had a signifi-cant effect on stress levels, said Peter Lercher, co-author of the study. Therefore, chronic exposure to nearby sounds from roads and train lines are a concern.
Females at Higher Risk from Noise Stress‑Study
When children have no control over prolonged exposure to noise, it can lead to "learned helplessness" syndrome – a condition linked to forms of depression and to poverty. "It's a pretty pervasive phenomenon," says Evans. He found that "girls exposed to the traffic noise become less moti-vated, presumably from the sense of helplessness that can develop from noise they couldn't control."
Women respond differently to loud noise, too. A study at Texas A&M University found that "women have a lower threshold to experience noise as stressful," according to psychologist Dr. Mary W. Meagher. "Our data suggest that women may be more sensitive to noise stress than men." While the women in the study were more easily "fright-ened" by a loud unexpected noise, the men were only more "startled."
British investigators found that a greater amount of neigh-bourhood problems, including noise, was associated with residents being three times as likely to say their physical function was impaired and twice as likely to report poorer
Noisy Neighbourhoods and Nuisance‑Reports
"The U.S. Census Bureau reports that Americans cite noise – more than crime, litter, traffic, or inefficient government – as the biggest problem affecting their neighbourhoods. 138 million people are regularly exposed to noise levels label-led as excessive by the Environmental Protection Agency."
health. "What we think is happening is that neighbourhood stress influences the biological processes that promote disease risk," said Dr. Andrew Steptoe of University Col-lege London.
Gary Evans and environmental psychologists at Cornell found that low‑level noise in open‑style offices seems to result in higher levels of stress, and lower task motivation.
Forty experienced female clerical workers (average age 37) were assigned for three hours to either a quiet office or one with low‑intensity office noise (including speech). The wor-kers in the noisy office experienced significantly higher lev-els of stress (as measured by urinary epinephrine, a stress hormone), made 40% fewer attempts to solve an unsolv-able puzzle, and made only half as many ergonomic ad-justments to their workstations, compared to their col-leagues in quiet offices.
Interestingly, however, the workers themselves did not report higher levels of stress in the noisy office. "But just because people fail to report that environmental conditions are negative, we can't assume that there are no adverse impacts," Evans says.
"Our findings resemble those in studies of very noisy en-vironments in that we found that realistic, open‑office noise has modest but adverse effects on physiological stress and motivation," says Evans, and might contribute significantly to health problems such as heart disease (due to elevated levels of epinephrine) and musculoskeletal problems. "Even low levels of noise can have a potentially stressful effect."
Stress and Memory
Chronic over‑secretion of stress hormones adversely af-fects brain function, especially memory. Too much cortisol can prevent the brain from laying down a new memory, or from accessing already existing memories.
The renowned brain researcher, Robert M. Sapolsky, has shown that sustained stress can damage the hippocampus, the part of the limbic brain which is central to learning and memory. The culprits are "glucocorticoids," a class of ster-oid hormones secreted from the adrenal glands during stress. They are more commonly know as corticosteroids or cortisol.
During a perceived threat, the adrenal glands immediately release adrenalin. If the threat is severe or still persists af-ter a couple of minutes, the adrenals then release cortisol. Once in the brain, cortisol remains much longer than adren-alin, where it continues to affect brain cells.