Kurt Fristrup is standing in the middle of a prairie and he’s the loudest thing for miles. He and I are huddled near an empty cattle pen in Pawnee National Grassland in northern Colorado. Before he pulled out his tools, the silence here was palpable. The breeze carried no sound except the rustle of a million stalks of yellow grass. A family of pronghorn, kind of like furry antelope, padded over to us to investigate.
Fristrup is disrupting this serene soundscape for a reason: He wants to better understand it—by recording it. Cows chewed through a microphone he set up a few months ago. And now he’s here to install a new one.
“My respect for those cattle has just gone up,” he says. “They gnawed through some of these things, and they’re pretty tough.”
Fristrup is a senior scientist with the National Park Service in Fort Collins, Colorado. And he’s tasked with protecting a natural resource. It’s not water or minerals or endangered species. It’s sound. Natural sound. His team is studying how man-made noise is drowning out the sounds of birds and insects and rain. And as more and more research links our well-being to what we hear, Fristrup and his colleagues are pointing to natural sound as something to be managed—and even protected.
“I’d like to think that we can reach out through this effort, not just to park visitors and not just to backpackers, but help everyone realize that their lives could be better and their communities could be more vibrant places if we take some time to make them quieter.”
LISTEN: “Why We Need to Hear the Sounds of Nature”
Most of us can probably agree—our world is pretty noisy. But just how noisy is something Fristrup is trying to figure out. For a decade, he and a small team of engineers, physicists and biologists have hidden microphones in parks around the United States. Some are really remote—think grizzly bears and back-country skiing. But others are in urban areas, like Civil War memorials and the Statue of Liberty.
Each microphone recorded 24 hours a day for a month, capturing fantastic sounds—like the trumpeting of elk and goofy birds called ptarmigans. Not to mention the grunts of bears destroying the microphones, which Fristrup says was totally worth it.
But what Fristrup was after was loudness. Each device measured decibel levels 33 times per second. That mountain of data fed a model that created a sound map of the contiguous United States. It took the qualities of each site, like how close it is to roads or water, and calculated median sound levels for the entire rest of the country—even places outside parks.
“You can see that it looks very much like the images of the earth at night from satellites. The brightest noise sources are concentrated in cities. Then you see these lines along the interstates and other major transportation corridors that also light up with sound.”
Kurt Fristrup repairs a damaged recording system on a cattle pen in Colorado’s Pawnee National Grassland. Photo: Kerry Klein
That big picture may not be all that surprising. But the differences in noise levels are staggering.
“You and I are standing about three feet apart, and you can comfortably hear what I’m saying. In the Sierra, the background sound levels are about 1,000 times lower, which means you could stand 90 feet away from me in the Sierra. I could talk at this level, and you could hear me just as clearly.”
Every rise of three decibels doubles the sound hitting our eardrums. Now consider this: The loudest places in the U.S. are around 40 decibels noisier than the quietest. So if you do the math, Manhattan can be around 8,000 times louder than Great Sand Dunes National Park—one of the darkest spots on the map.
“There are times when I’ve been in the field in the intermountain west, where I’ve not only been able to hear my own heartbeat, but I’ve been able to hear the heartbeat of the person in the field with me.”
Our biggest noise producer is transportation—cars, trucks, motorcycles. Even the hiss of tires against pavement. But even far away from roads, there are still airplanes. Fristrup estimates man-made noise really took off in the mid-20th century, when flying became commonplace. Now, most of us are so used to planes, we don’t even notice them. After hiking with friends, Fristrup likes to ask how many they heard.
“Most people will say, ‘You know, I think I heard one or two aircraft.’ And, being me, I’ve actually been counting the whole day and I’ll say, ‘Well, we actually heard 21 high-altitude jets, 10 propeller aircraft and two helicopters.’”
So if we’re not even conscious of the man-made noises around us, then what’s the big deal? Researchers at Penn State are trying to figure that out.
“In the Sierra, the background sound levels are about 1000 times lower, which means you could stand 90 feet away from me in the Sierra. I could talk at this level, and you could hear me just as clearly. There are times when I’ve been in the field in the intermountain west, where I’ve not only been able to hear my own heartbeat, but I’ve been able to hear the heartbeat of the person in the field with me.”
Heather Costigan, a lab manager at Penn State, outfitted me with a monitor that continuously recorded my heart rate for an experiment they’re conducting. It was informally called “the soundscape study.”
The first step was stress. I had to imagine I was applying for a big job and gave a five-minute speech in front of a one-way mirror. It was kind of intense. Then came the soundscape. Costigan whisked me into a dark room. I put on headphones and settled in to watch a video. On the screen was Half Dome, the majestic centerpiece of Yosemite Valley. The sun crept across the granite. Red and yellow leaves fluttered. But when I heard a garbage truck interrupt, and then a motorcycle, I cringed.
“We would like to know, when is sound helpful, when is noise harmful, under what circumstances and for what people?” says Joshua Smyth, a professor of biobehavioral health at Penn State who’s coordinating the soundscape study.
His hypothesis is that natural sound will speed up stress recovery, even with people making noise in the background. But some test subjects watched that video with no man-made sound at all, and Smyth thinks they’ll recover even faster.
For each test subject, he and Costigan tracked heart rate and also measured cortisol—a hormone in saliva. Cortisol is a kind of stress indicator, and chronically stressed people produce a lot of it. Studies have connected that highly stressed state with all sorts of health issues—heart problems, breathing problems, musculoskeletal problems and a higher susceptibility to viruses and infections.
“So we just generally see a decay in the capacity of the body [in] response to these sort of chronic conditions of stress,” Smyth says.
So when we hear irritating sounds, even if we try not to let them bother us, Smyth suspects that our stress levels still spike, priming our bodies for other health problems. But could noise ever be so bad that it alone breaks down our immune defenses? Probably not.
“But, if I have that and stress from work and not a particularly supportive relationship and I’m worried about money, then collectively, I may be at risk.”
Joshua Smyth, a biobehavioral health professor at Penn State, is interested in how the human body responds to what it hears. Photo: Kerry Klein
So our cars, our airplanes—some of the very advances that make our lives easier and more productive—they might also be sabotaging us. So what’s the solution? Stop driving? Renounce technology? A social scientist across campus offers a gentler perspective.
“I think that talking about the positive effects of nature sounds is a much better story than talking about the negative impacts we have on the world,” says Peter Newman, who heads up Penn State’s department of Recreation, Park and Tourism Management. “Both might be true, but we know that we can focus on the fact that it’s important to us and it resonates with people. No pun intended.”
Newman is studying why people visit parks and what they do once they’re there.
“Listening is a huge part of that experience that people have out there. They want to hear the noises of wildlife, they want to hear the sounds of wind and water. And those are really important things for how they feel.”
In the past, studies have shown we recover better from surgery when we can see nature. Newman says we also benefit from hearing it. Research shows natural sounds can improve cognition, mood and general well-being. And that’s an idea a lot of people already buy into. It’s easy to find recordings of relaxing nature sounds.
But Newman argues that we can preserve sound in the real world too. He points to a success story in Muir Woods, a national monument outside San Francisco. In an experiment in 2009, he and a few colleagues posted signs for quiet zones and showed visitors how to be less noisy.
“We actually were able to reduce the amount of noise there by about three decibels, which was the equivalent of doubling people’s listening area,” Newman says.
Conserving sound in parks may seem to be at odds with the Park Service mission of bringing people there. But back in Colorado, Kurt Fristrup sees these opposing values as a challenge. He knows the solution isn’t to keep people away. Instead, he’s helping develop new technology. Like quieter pavement and electric airplanes that could someday lead silent air tours. His team is also developing roadside noise gauges, kind of like the blinking signs that tell you how fast your car is moving, only it’s how loud you are.
“I look at this as an enormous opportunity to improve not only resource conditions in parks, but the quality of the environments in which we all live,” Fristrup says. “Because unlike many other forms of pollution, all of this goes away as soon as we throw the switch.”
Throwing that switch won’t be easy, but we all have an incentive to try. Because who wants a world in which recordings of nature are our only option? So next time you’re outside, turn off your car, stop talking and listen. What you hear might just be good for you. And it’s free. For everyone. Natural sound is a truly infinite resource. All we have to do is not drown it out.
Kerry Klein is a science reporter based in California. This story is a production of the STEM Story Project, which is distributed by PRX and made possible with funds from the Alfred P. Sloan Foundation.