The official word for the human-made soundscape is the anthrophone. Can you hear it? “Noise” is unwanted sound, and levels from human activities have been doubling about every 30 years, faster than population growth. Traffic on roads in the United States tripled between 1970 and 2007. According to the U.S. National Park Service, 83 percent of the land in the Lower 48 states sits within 3,500 feet of a road, close enough to hear vehicles. For planes, the figures are even more dramatic: The number of passenger flights has increased 25 percent since just 2002, and 30,000 commercial aircraft fly overhead per day. In 2012, the Federal Aviation Administration predicted an astounding 90 percent increase in air traffic over the next 20 years. Human activities in general increase background noise levels by about 30 decibels.
Stats like those dismay Gordon Hempton, a sound engineer based in Washington State who decided to travel the country in search of the few remaining quiet places. By his count, the entire continental United States has fewer than a dozen sites where you can’t hear human-made noise for at least fifteen minutes at dawn. That’s a pretty ridiculously low bar. But it is still so out of reach. The quietest place in the country, Hempton discovered, is a spot in the Hoh Rainforest at Olympic National Park. If you want to hear the earth without us, it’s marked by a red stone on a moss-covered log at 47-degrees 51.959N, 123-degrees 52.221W, 678 feet above sea level. But get there early; by midday, even there, you can hear overflights a dozen times per hour. Noise may well be the most pervasive pollutant in America.
I never thought much about airplane noise until I moved to D.C. Out West, the planes were fewer and farther away. But my neighborhood now is one of the loudest in the city thanks to flights following the Potomac River as they roar in and out of Reagan National Airport. Jets fly overhead at a rate of about one every two minutes starting early in the morning, with average decibel levels between 55 and 60 but sometimes spiking much higher. As reference, 60 decibels is high enough to drown out normal speech; over 80 can damage hearing.
Moving in, the neighbors assured me I would learn to ignore the planes. “After a year or so, you don’t hear them anymore,” they’d said. But it’s been over two years now and I still hear the planes. They drive me crazy. It’s hard to eat alfresco, impossible to talk on the phone with the backdoor open. Between the planes and the routine security surveillance choppers, I feel like I’m in a militarized zone when I walk near the river. My gaze is drawn up, and I can read the logo on the fuselages. Sometimes, I can even make out the theme animal on the Frontier Airlines tail fins. There’s the mustang! It’s wildlife viewing, D.C.-style.
The logical thing would be to go the hell back to Colorado. But my neighbors aren’t exactly wrong. People can become habituated to sound, at least partly. We’ve all heard stories of people who say they can’t sleep if it’s too quiet, or they can’t work apart from a din. Some writers have apps that replicate the sounds of a coffee shop. I know a New Yorker who now lives in the country, but he plays himself devotionally made recordings of 14th Street, sirens and all, to fall asleep at night.
I keep hoping that I will become inured or even nurtured somehow by the city sounds, but it isn’t happening. In fact, I’ve learned that full habituation is a bit of a pipe dream. Just because you don’t notice certain noises anymore doesn’t mean your brain is not on some level responding to them. Noise poses risks far beyond our ear canals. In fascinating studies, people have been hooked up to electrocardiogram monitors while sleeping through plane, train, and traffic noise. Whether or not they woke up, their sympathetic nervous systems reacted dramatically to the sounds, elevating their heart rates, blood pressure, and respiration. In one study that lasted three weeks, the subjects showed no biological signs of habituating to the noise, and in another study that lasted for years, the biological effects only got worse.
THIS SUBCONSCIOUS VIGILANCE makes sense from an evolutionary standpoint. Sleeping or hibernating animals must maintain their capacity to react to danger. Sound is our main “alerting” and “orienting” sense; it tells us not only that something is out there, but also from which direction it’s coming. Sound also triggers our strongest startle reactions.
Of course, nature didn’t intend roaring jet aircraft to be processed by our nervous systems every sixty seconds. What does a loud anthrophone do to us? The news is not good, not for us and not for the birds, whales, and other wildlife whose breeding and foraging habits are upended by it. Numerous whale die-off events have been attributed to navy sonar, the vibrations from which literally cause their heads to explode. In the remote backcountry of Yosemite National Park, aircraft are audible 70 percent of the time, raising ambient noise levels by about five decibels. That’s enough to reduce the distance at which prey species can hear a predator approaching by 45 percent.
The brain processes sound swiftly. Sound waves travel through air and collide with our eardrums, which wiggle back and forth in response to volume and amplitude. Nerve cells pick up these perturbations and send signals to our auditory cortex, the brain stem, and the cerebellum, which together process fear, arousal, and motion. As to the perennial question of whether a tree falling in the forest makes a sound if no one is there to hear it, the answer is technically no. There is no sound apart from a sentient brain’s interpretation of molecules vibrating through air or water.
It’s difficult to know which came first in evolution: the ability to hear or the ability to see, but fish are thought to have developed vibration-sensitive hairs hundreds of millions of years ago, before they could see. The fancy three-boned middle ear of mammals is—along with mammary glands—our defining trait. In the womb, we can hear before we can see. By birth, hearing is our most fully developed sense. Because sound waves vibrate through bones and the brain, it is a 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, 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 micro stresses 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. 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 European deaths per year to heart attack and stroke caused by high levels of background noise.
In the largest and scariest study to date looking at noise pollution and children’s cognition, researchers followed several thousand children attending elementary schools near major airports in the U.K., Spain, and the Netherlands. They found significant impacts on reading comprehension, memory, and hyperactivity. The results were linear: for every five-decibel increase in noise, reading scores dropped the equivalent of a two-month delay, so that kids were almost a year behind in neighborhoods that were 20 decibels louder (results were adjusted for income and other factors). There’s something real to the phrase “you can’t hear yourself think.”
After reading the studies, I loaded a decibel meter app on my phone. Distressingly, my home noise levels are comparable to those associated with hypertension and learning delays. I asked for noise-canceling headphones for Christmas.
THE U.S. NATIONAL PARK SERVICE is uncommonly interested in noise pollution because it operates under a federal mandate to protect its resources, including, since 2000, natural soundscapes. It’s practically an impossible task, but as bioacoustical scientist Kurt Fristrup points out, a little bit of noise regulation can go a long way. Fristrup coordinates the science at the rather romantic-sounding Natural Sounds and Night Skies Division of the agency. Fristrup’s research includes not only documenting the ill effects of anthropogenic noise on visitors and wildlife, but also documenting the beneficial effects of its absence.
To learn more about how sound changes our brains and to find out just how noise-sensitive I am, I ventured to the sound labs of Pennsylvania State University. I was met by Peter Newman and Derrick Taff, two young park-rangers-turned-social-scientists in the Department of Recreation, Park, and Tourism Management who work with Fristrup’s group. Newman didn’t start out studying sound, he explained to me as we navigated a noisy cafeteria on campus. He was interested in parks and crowds, and was conducting visitor surveys at Muir Woods National Monument, known for its ancient redwoods.
“We asked if there was one thing to fix about the park unit, what would it be?” he explained. “And people said they wished it were more quiet. I was surprised what a big deal it was, but these were old-growth forests with a primeval feel, and visitors felt it should be quiet. Later we went back and analyzed the words they used, and they were so emotion-laden. Words like ‘soothing,’ ‘peaceful.’ That was interesting to us. That’s where the research started dipping its toes into public health.” And the survey carried weight: Muir Woods now has a “quiet zone,” like the Amtrak quiet car: no phones; soft voices only. The Muir Woods quiet zone reduced the background noise there by three decibels, which is enough to double the listening area. So instead of hearing birds something like 10 yards in front of you, now you can hear them 20 yards away.
Now Newman and Taff run experiments out of the university’s Acoustics Social Science Lab, the acronym of which, people noticed, resembles asshole, so they’re switching the name around. Among other results, Newman and Taff and their colleagues have discovered that human-caused noise actually makes parks look worse, not just sound worse. Visitors hearing loud vehicle noise rate parks as 38 percent less scenic than those who don’t hear it (motorcycle sounds had the most impact, followed by snowmobiles and propeller planes). Counterintuitively, the soundscape was affecting the views.
Veering into human health, Newman and Taff decided to team up with Joshua Smyth, a biobehavioral health psychologist also at Penn State. He’s interested less in how sound messes with your psyche and more interested in how it can make you feel better. Can some sounds be an intervention or an antidote for stress and depression? To tease out how sound affected me, Smyth ran me through his current experiment. First he hooked me up to a heart rate monitor to wear throughout. Then he gave me the Weinstein Noise Sensitivity Scale test, which asked a bunch of questions about my attitudes to various types of noise from things like a stereo to street traffic. I scored a 5.2. Adults average a 4, and college students average a 3.5, which puts me in the 88th percentile of sensitivity to noise. No surprise there.
Next, I spit into a test tube to provide a reading of my pretest cortisol levels. Now the real fun would begin. In order to tell if nature sounds help “restore” subjects psychologically, Smyth has to first stress them out. Public speaking and math tests are two of the most dreaded tasks shared by a large number of people. So I was handed a pen and some paper and told to prepare a short speech. Partway through, my notes were abruptly taken away from me and I was told to stand and deliver the speech to a large mirror, behind which sat a panel of faceless judges. Several times during the five-minute speech, I was interrupted and told to speak up. As I later discovered, this gauntlet of misery is called the Trier Social Stress Test. Even though I knew there was no panel of judges, I still showed a textbook response, with my heart rate climbing from the mid-60s to the mid-90s during the speech, and my cortisol levels (as revealed later) rising from 6.7 nanomoles per liter to 12.1. It’s reductive to call cortisol a stress hormone, but lower levels generally mean lower stress.
Next, Smyth randomly assigns subjects to one of three recovery exercises: watching a fifteen-minute nature video with nature sounds, watching a fifteen-minute nature video with nature sounds and motorized sounds, or just sitting in a quiet room with no video. My video started playing, a simple scene from Yosemite of a summer meadow, some chirping birds, a blue sky. But a couple of minutes in, I heard a truck engine, followed by quiet, followed by the sound of a propeller plane. I’d been assigned to the second condition, and I again displayed a textbook response: once the nature video started, my heart rate immediately sank to baseline mid-60s range. When the truck rumbled, however, my heart rate shot up ten points. It took a while for it to drop again, but after more quiet nature, it plummeted down to the mid-50s. Now I was so relaxed I was practically dead. When noise #2 appeared, my heart rate shot back up, though not as high as the first time.
The test showed that it’s simply harder for someone who is noise-sensitive to fully unwind in an urban environment, regardless of its nice parks and nesting ducks. As Smyth put it: “Your recovery was clearly disrupted by the experience of noise. It set back your recovery with a carryover effect of at least a minute. For you, walking in the park, the benefits of nature may be offset by the noise of planes. Those noises are violating your experience of pleasant views and sound. It’s half as stressful as doing the speech task. Those aren’t trivial effects.”
Based on his research, Smyth has several recommendations: try to reduce exposure to irksome noise through headphones, office insulation, etc.; if we can’t do that, try to change our attitude about the noise—maybe by thinking that someday I will be on one of those planes getting the hell out of D.C.—and make an effort to experience positive sounds and quiet places.
In fact, Smyth thinks short nature-based interventions could help more people more efficiently than many other fixes that get more attention, like meditation. “Meditation is getting all the glory. Unjustifiably,” said Smyth. “Seventy percent of people will wash out.” Not everyone likes nature either, but just about everyone likes the noise to die down, at least occasionally. “We should think about soundscapes as medicine,” he says. “It’s like a pill. You can prescribe sounds or a walk in the park in much the way we prescribe exercise. Do it twenty minutes a day as a lifetime approach, or you can do it as an acute stress intervention. When you’re stressed, go to a quiet place.”
Excerpted from The Nature Fix: Why Nature Makes Us Happier, Healthier, and More Creative, by Florence Williams. Copyright © 2017 by Florence Williams. With permission of the publisher, W. W. Norton & Company, Inc. All rights reserved.