On a spring afternoon in Bankers Hill, San Diego, the
soundscape is serene: Sea breeze rustles through the trees, and neighbors chat
pleasantly across driveways.
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Except for about every three minutes, when a jet blazes
overhead with an ear-piercing roar.
A growing body of research shows that this kind of chronic
noise — which rattles the neighborhood over 280 times a day, more than 105,000
times each year — is not just annoying. It is a largely unrecognized health
threat that is increasing the risk of high blood pressure, stroke, and heart
attacks worldwide, including for more than 100 million Americans.
We’ve all been told to limit the volume on our headphones to
protect our hearing. However, it is the relentless din of daily life in some
places that can have lasting effects throughout the body.
When it gets too noisy
Anyone who lives in a noisy area, like neighborhoods near an
expressway, may feel they have adapted to the cacophony. The data,
however, shows the opposite: Prior noise
exposure primes the body to overreact, amplifying the negative effects.
Even people who live in relatively peaceful rural and
suburban communities can be at risk. The sudden blare of trains that run
periodically through D’Lo, Mississippi (population: fewer than 400), can be
especially jarring to the body because there is little ambient noise to drown
out the jolt.
We went to neighborhoods in rural Mississippi, New York
City, and suburban California and New Jersey to measure noise exposure and ask
residents about the commotion. We consulted more than 30 scientists and
reviewed thousands of pages of research and policies to examine the pathology
and epidemiology of noise.
Effects on the bodyA siren shrills. A dog barks. Engines thrum. Jackhammers
clack.
Unpleasant noise enters your body through your ears, but it
is relayed to the stress detection center in your brain.
This area, called the amygdala, sets off a cascade of
reactions in your body. If the amygdala is chronically overactivated by noise,
the reactions begin to produce harmful effects.
The endocrine system can overreact, causing too much
cortisol, adrenaline and other chemicals to course through the body.
The sympathetic nervous system can also become
hyperactivated, quickening the heart rate, raising blood pressure and
triggering the production of inflammatory cells. Over time, these changes can
lead to inflammation, high blood pressure and plaque buildup in arteries,
increasing the risk of heart disease, heart attacks and stroke.
When researchers analyzed the brain scans and health records
of hundreds of people at Massachusetts General Hospital, they made a stunning
discovery: Those who lived in areas with high levels of transportation noise
were more likely to have highly activated amygdalae, arterial inflammation and
— within five years — major cardiac events.
The associations remained even after researchers adjusted
for other environmental and behavioral factors that could contribute to poor
cardiac health, like air pollution, socioeconomic factors and smoking.
In fact, noise may trigger immediate heart attacks: Higher
levels of aircraft noise exposure in the two hours preceding nighttime deaths
have been tied to heart-related mortality.
What Is too loud?
Sound is often measured on a scale of decibels, or dB, in
which near total silence is zero dB and a firecracker exploding within a meter
of the listener is about 140 dB.
We used a professional device called a sound level meter to
record the decibel levels of common sounds and environments.
Compared with a quiet room, a passing freight train peaks at
about four times as many decibels. But the difference in how loud the train
sounds to the ear is much more dramatic: The train sounds more than 500 times
as noisy.
That’s because the decibel scale is logarithmic, not linear:
With every 10 dB increase, the sense of loudness to the ear generally doubles.
And that means regular exposure to even a few more decibels of noise above
moderate levels can set off reactions that are harmful to health.
According to the World Health Organization, average road
traffic noise above 53 dB or average aircraft noise exposure above about 45 dB
are associated with adverse health effects.
Nearly a third of the US population lives in areas exposed
to noise levels of at least 45 dB, according to an analysis based on models of
road, rail and aircraft noise in 2020 from the Department of Transportation.
Mounting research suggests that the relationship between
noise and disease is eerily consistent: A study following more than four
million people for more than a decade, for example, found that, starting at
just 35 dB, the risk of dying from cardiovascular disease increased by 2.9
percent for every 10 dB increase in exposure to traffic noise.
Scientists believe that pronounced fluctuations in noise
levels might compound the effects on the body.
They suspect jarring sounds that break through the ambience
— recurring jet engines, a pulsating leaf blower, or the brassy whistle of
trains — are more detrimental to health than the continuous whirring of a busy
roadway, even if the average decibel levels are comparable.
Swiss researchers measured and compared transportation noise
along a highway with a railroad track, over the course of a night. They found
that the highway and the railroad had the same average decibel level over the
eight-hour night. But while the hum of the highway remained relatively steady
throughout the night, the periodic passing of trains caused far more dramatic
variation, a sound quality linked to harm.
In a subsequent Swiss study, higher degrees of nighttime
“noise intermittency” — or the extent to which sound events were
distinguishable from the background levels — were associated with heart
disease, heart attacks, heart failure, and strokes.
What can be done?
Fifty years ago, under the Noise Control Act of 1972, the
newly formed Environmental Protection Agency was a trailblazer in recognizing
the danger of noise: It educated the public, established safety limits,
published analyses on various culprits, and recommended actions to mitigate
harm.
But its office of noise abatement was defunded by the Reagan
administration, rendering policies unenforceable and regulatory criteria
obsolete. The Occupational Safety and Health Administration’s eight-hour
workplace noise limit is still 90 dB.
Protection against noise would be economically advantageous.
Economists who analyzed health care spending and productivity loss because of
heart disease and high blood pressure have argued that a 5 dB reduction in US
noise could result in an annual benefit of $3.9 billion.
Unlike most other contributors to heart disease, noise
cannot be addressed fully between a patient and a doctor. Protection requires
changes in local, state, and federal policy.
In the meantime, in D’Lo, George Jackson has repeatedly
jacked his home to decrease the vibration. In Mendenhall, Mississippi, Carolyn
Fletcher resealed her windows. In Bankers Hill, Ron Allen takes vitamin
supplements and plugs his ears.
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