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Quiet, please!
Noise pollution can damage your health and shatter your peace of mind. Here’s how to turn it down.
“It is important to differentiate between effects like hearing loss and stress effects like high blood pressure, because two different sound sources are concerned,” says Wolfgang Babisch, senior research officer at the German Federal Environmental Agency in Berlin. “On the one hand, there is industrial noise and leisure-activity noise—things such as rock concerts, discos and iPod use—that can cause various degrees of hearing loss and/or tinnitus [a persistent ringing in the ears]. Studies have shown, for instance, that noise levels of more than 100 decibels are absolutely normal on today’s dance floors, and young people often complain of hearing problems as a result. On the other hand, there is the so-called environmental noise caused by road or aircraft traffic. Since the sound level is lower in these instances, there are usually no adverse effects on hearing. But they can affect the whole organism by triggering stress responses.”
Cars and trucks produce noise in two ways. The engines make noise, and the contact between the vehicle and the road creates noise. At speeds greater than 40 mph (60 km/h), road noise is louder than engine noise.
Trains and other forms of rail transportation make lots of noise too. That unendurable wheel squeal happens when the train goes around tight curves, which are more common in crowded cities. Train stations are noisy because of running engines, engine whistles and loudspeaker systems. High-speed trains, those that travel faster than 155 mph (250 km/h), can mimic the acoustic effect of a low-flying jet directly overhead.
Speaking of jets, it’s not just the noise that’s disturbing; it’s, but the vibration and rattle they cause at low altitudes. Ask people who live near New York City’s La Guardia Airport. According to a study published earlier this year in the Journal of Occupational and Environmental Hygiene, people living three-quarters of a mile from this airport are exposed to four times as much noise as people living five miles away. Among people whose homes were in the flight path, 55 percent said they were bothered by the noise.
But airports don’t just have planes; they also draw road traffic, and even more people, 63 percent, said they were bothered by road noise leading into and out of the airport. The noise measured in this study translated “to a sound that is perceived to be roughly twice as loud as a more or less constant background noise level in the home,” says Beverly Cohen, a professor at the Nelson Institute of Environmental Medicine at the New York University School of Medicine, and one of the investigators involved in this study.
The sounds of construction, especially in cramped urban areas, are another major contributor to noise pollution—pneumatic hammers, air compressors, bulldozers, loaders, dump trucks and pavement-breakers. Hospitals can be as noisy as construction sites, and a recent study conducted at the Queen’s Medical Centre in Nottingham in the UK makes it difficult to believe that people are expected to recover from illness there. The WHO guidelines for hospitals stipulate that neither daytime nor nighttime noise levels should exceed 30 and 40 dBA respectively. Noise in the Nottingham hospital was measured and analyzed over a 24-hour period on five general surgical wards. On all of them, peak noise levels exceeded 80 dBA during the day. On one ward, the peak level was an astounding 95.6 dBA. That’s like having a cement truck drive past your bed—repeatedly.
Similar results come from a study performed in Madurai, India, in which the obstetrics and gynecology unit was the noisiest (72 dBA) and the quietest was the morgue (57 dBA). At least the patients in the morgue are less likely to complain.
It’s a staple of cartoons and sitcoms: A red-faced guy is sitting in a chair trying to read the paper, but the veins in his temple are bulging and steam is coming out of his ears because of a) noisy neighbours, b) a barking dog, c) a jackhammer, or d) planes flying overhead. The steam out the ears is an exaggeration; the bulging veins aren't. Chronic exposure to loud noise is bad for the cardiovascular system.
Researchers with the Hypertension and Exposure to Noise near Airports (HYENA) project in cities across Europe conducted blood pressure measurements at 15-minute intervals, or about 30 measurements each night, in 140 people sleeping near major airports. Noise levels were measured at the same time. Even when the overhead airplane noise didn’t wake the study participants, systolic blood pressure (the top number on a blood pressure reading) increased by 6.2 mm Hg and diastolic blood pressure (the bottom number) by 7.4 mm Hg. Heart rate went up by an average of 5.4 beats per minute. For someone whose blood pressure is generally in the low or normal range (120/80 mm Hg or lower), this might not be hazardous. But for people whose blood pressure is already too high, these constant spikes may increase the risk of stroke, heart attack or heart or kidney failure.
Blood pressure and heart rate reactions “were similar regardless of the noise source—aircraft, truck, or partner snoring,” says Lars Jarup, a researcher with the Imperial College of London, England, and one of the principal investigators. That’s right—a partner snoring is right up there with aircraft noise as a cause of nighttime blood pressure spikes.
“We believe that it is likely that frequent repeats of nightly acute blood pressure elevations will affect blood pressure chronically, but that needs to be studied further,” says Jarup, who adds there’s no evidence that people become habituated to a noisy sleeping environment.
“Long-term exposure to environmental noise, especially at night, causes chronic disturbance of the natural sleep pattern—even if you don't wake up completely,” says Babisch of the German Federal Environmental Agency. “Studies in sleep labs have proved that persons exposed to this type of noise show increased levels of the stress hormones adrenalin and noradrenalin. These hormones regulate metabolic functions that affect risk factors such as the blood fat level and blood sugar level.”
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As a teacher, thank you for speaking up about students, learning and noise. Some people think I run a tight ship because my classroom is quiet when they enter, but my students talk when they want, but quietly and appropriately. They understand the need for less noise and in fact as the year progresses they choose having a calm and quiet environment. Most of my students are disadvantaged, live in crowded conditions, this is probably the only quiet they have during their day. Who ever said quiet was a bad thing?
posted by blaber on 7/14/2008 12:10 pm