sense we feel with our whole being.
It’s only after sound signals wash through our limbic brains that
the frontal cortex gets to weigh in, for example interpreting the big
rumbles as a familiar DC-10, not a marauding lion. In the
microseconds in between, though, a stress response has already
begun. If, as Stanford neuroscientist Robert Sapolsky points out, lots
of microstresses administered in a slow drip over time add up to
chronic stress, then even something as harmless as airplanes heard
during sleep can accrue in the stress bank.
Epidemiological and case-control studies overwhelmingly back up
this observation. Many have been carried out in Europe, where high-
density neighborhoods surround busy airports and where excellent
health records are easy for researchers to access. In a study of 2,000
men over age 40, environmental noise above 50 decibels was
associated with a 20 percent increase in hypertension. In another
study of 4,800 adults over age 45, every 10-decibel increase in
nighttime noise was linked to a 14 percent rise in hypertension.
Health experts studying nearly a million people living near the Bonn
airport found that women living with noise over 46 decibels were
twice as likely to be on medication for hypertension as those living
with levels under 46 decibels. The World Health Organization
attributes thousands of deaths per year in Europe to heart attack and
stroke caused by high levels of background noise.
Researchers followed hundreds of children over two years before
and after an international airport opened in Munich. They also looked
at a control group of similar children who did not live as close to the
airport. The stress hormones epinephrine and norepinephrine nearly
doubled in the noisy-hood kids measured at six and eighteen months
after the flights began. Their systolic blood pressure went up five
points (the quieter-neighborhood kids’ blood pressure went up two
points).
In the largest and scariest study to date looking at noise pollution