The constant roar of traffic, incessant construction noise, piercing sirens, honking horns, shrieking loudspeakers — noise in cities is clearly a nuisance.
However, it is also a danger.
The WHO has described noise pollution as an underestimated threat that can cause hearing loss, cardiovascular problems, cognitive impairment and stress.
Illustration: Yusha
“Noise pollution causes hypertension, diabetes, obesity, heart attacks, strokes and death,” said Daniel Fink, chairman of the Quiet Coalition, a community of health and legal professionals concerned with the adverse effects of environmental noise.
Noise pollution is often cited as one of the main factors reducing quality of life in large, 24-hour cities, such as New York City — where more than 200,000 noise complaints were recorded in 2016. It causes stress, which has its own adverse effects on health.
While the effect of noise on mental health has not been studied extensively, a paper published in journal PLOS One by scientists from Johannes Gutenberg University in Mainz, Germany, said that “strong noise annoyance is associated with a twofold higher prevalence of depression and anxiety in the general population.”
A study by experts at the American College of Cardiology linked noise pollution to increased cardiovascular problems — high blood pressure, heart attacks, stroke and coronary heart disease — through the body’s stress mediated response, resulting in the release of the stress hormone cortisol, which in turn damages blood vessels.
At a conference on noise organized by the European Commission in April last year, noise was described as “the silent killer” with potentially severe consequences for our physical and mental health.
And yet its effects remain unreported and underestimated.
Eoin King, an assistant professor of acoustics and author of the book Environmental Noise Pollution, calls noise the ignored pollutant.
“Environmental noise still continues to be poorly understood by practitioners, policymakers and the general public,” he said.
Most worrying is the effect on children, King said.
“Studies considering the effect that noise may have on children have found that tasks such as reading, attention span, problem-solving and memory appear to be most affected by exposure to noise,” he said.
The issue is compounded by debate over how much noise it is safe to be exposed to.
In its Make Listening Safe guide, the WHO says that 85 decibels (dB) is considered the highest safe exposure level, up to eight hours.
However, others — Fink among them — have said that is still too loud.
A car measures 70dB, a jackhammer 100dB and a plane taking off 120dB, the WHO said.
“Though there is no set threshold to establish risk, we do know that anything above 60dB can increase risk for heart disease,” Thomas Muenzel from the Mainz University Medical Center said.
A BBC report found that parts of the London Underground were “loud enough to damage people’s hearing,” with noise levels greater than 105dB on many lines.
Some were “so loud they would require hearing protection if they were workplaces,” the report said.
Concerned about the risk of hearing loss in cities, Mimi Hearing Technologies last year created a World Hearing Index to draw attention to the issue.
With the results of hearing tests of 200,000 of their users worldwide and data on noise pollution from WHO and Sintef, a Norwegian research organization, the index plotted levels of noise pollution and hearing loss in 50 cities.
The study found that, on average, a person living in the loudest cities has hearing loss equivalent to that of someone 10 to 20 years older.
Overall, the results showed a 64 percent correlation between hearing loss and noise pollution.
Guangzhou, China, ranked as having the worst level of noise pollution in the world, followed by Cairo, Paris, Beijing and Delhi. Of the 50 cities, Zurich was found to have the least noise pollution.
Participants in Delhi recorded the highest average hearing loss — equivalent to someone 19.34 years older than them. Vienna had the lowest hearing loss, but still, on average, that of someone 10.59 years older.
“We were able to collect quite a unique hearing data warehouse on hearing abilities across countries and continents,” Mimi managing director Henrik Matthies said. “There is an obvious known correlation between being exposed to noise and decreased hearing ability.”
“However, mapping this correlation to cities helped us to get the message out, sparking a debate about noise pollution and hearing in megacities like Hong Kong and Delhi,” he said.
What can be done about it?
“The EU are probably the world leaders at setting out a process to tackle noise pollution,” King said.
In 2002, it issued an environmental noise directive that requires member states to map noise exposure in urban areas holding up to 100,000 people to develop noise-abatement action plans in these areas and preserve quiet areas.
Action plans usually incorporate a variety of measures, such as traffic management strategies, promoting light rail systems and electric buses, reduced speed limits, introducing noise barriers and improved planning processes.
However, good intentions only go so far.
“The problem is that there is no real enforcement associated with these action plans,” King said. “Until there is more of a political will to drive planning decision related to noise, I don’t think much will change.”
With road traffic by far the largest source of noise pollution in Europe, affecting an estimated 100 million Europeans, concepts like Paris’ car-free day could have an effect.
For one day every month in the French capital, 30 percent of the city becomes off-limits to vehicles. The project has seen sound levels in the city center drop by half.
“The most effective way to control noise is at the source. If we could make planes, trains and cars quieter, we would solve a lot of our problems,” King said. “If all vehicles in a city street were electric, noise would be significantly reduced.”
Increasingly, citizens can also do their bit to monitor noise pollution in cities by transforming their smartphones into sound level meters.
The NoiseTube app, developed by researchers at the Free University of Brussels, enables users to record where and at what times noise levels are highest to produce a detailed “noise map” of the city. Councils can use the data to target noise pollution more effectively, using sound-absorbent materials such as foam and fiberglass where they are needed most.
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