With summer on the horizon, maybe you’re hoping to find some peace and quiet in the great outdoors. Where you find it can be a challenge. Luckily, the National Parks Service has a map tracking noise pollution throughout the United States.
Actually, there’s two maps. One that tracks the current state of sound in the U.S., and another that maps what the country would sound like without humans and all of our racket. While the latter is certainly fascinating, it’s the former that’s meant to be a powerful tool for conserving natural spaces.
“[The mapping] helps us understand the extent of noise in the United States - how broadly it’s distributed - and where we might focus our attention in order to restore soundscapes to something like their natural condition,” said Kurt Fristrup, a researcher with the park service’s Natural Sounds and Night Skies Division who spearheaded the idea.
Some sounds interfere with visitors’ experience of the parks and other natural spaces. Think of planes flying overhead.
“There’s nowhere in the lower 48 where you can sit in a national park or any other natural area and not hear aircraft,” he said. “There’s no such thing as a noise-free day anywhere.”
The good news is that wildlife aren’t generally affected by that type of noise. Human ears are tuned to low frequency sounds like the ones emitted by planes, so it’s backpackers and campers who are inconvenienced by overhead flights.
The same is not true with the sounds of roadways, however.
When an animal hears road noise, like cars zooming by or the beeping of trucks backing up, they go on the alert. The more time they spend in that state, the less time they spend on gathering food or caring for their young. Fristrup said animals in environments like this sometimes weigh less, build fewer nests or suffer from dulled instincts due to the hum of human activity.
To demonstrate, Fristrup took me on two hikes. The first was to Bobcat Ridge, grasslands that are sort of walled in by huge red rock ridges found southwest of Fort Collins. Western meadowlarks flitted between leaning stalks of burdock. Though they were several feet away from us, the birdsong projected so far, it sounded like they were right behind us. Magpies darted from tree to tree. Over a hill, we could hear the loud croaking of a chorus of frogs. Overhead, the sky was clear... except for the jets crisscrossing overhead. Fristrup couldn’t help counting them.
“There’s our fifth jet overflight,” he said when we stopped to look out at a valley. “It’s an occupational hazard I have now, I keep count of aircraft noise that I hear.”
Still, Bobcat Ridge is fairly quiet by Fristrup's measurements - or as he calls it “acoustically isolated.” By contrast, the Fort Collins Environmental Learning Center across town and south of busy Prospect Ave. was noisier.
Crossing the creaky footbridge over the Poudre River, the drone of the adjacent water treatment facility faded into the distance. The beeping from nearby construction vehicles gradually became faint, but proved to be inescapable.
Further down the trail, many of the noises of the city came to be replaced with the loud rush of the Poudre, its waters high from recent rains and runoff. Fristrup said the parks service’s map doesn’t just pick up man made noise. It detects natural noise - and bodies of water tend to occur in areas with more lush vegetation, which attracts more animals. Which means more noise.
That’s why there are two maps; to differentiate between zooming cars and rushing rapids. Dan Mennitt, the park service researcher behind the maps, notes that there’s a diversity of natural soundscapes when you look across the country.
“We’ve got volcanic craters on Hawaii, some of the quietest places we’ve measured,” Mennitt said. “They’re so quiet, they’ve defied our ability to actually measure them. And then at the same time, there’s places like the everglades that are just teeming with life, and all throughout the night, you can have insect choruses that are quite vibrant and loud. At the same time, we also have that diversity from small towns, larger cities and everything in between.”
Indeed, capturing the sounds of towns and cities was important context for data collected in natural areas. This marks a first for the parks service - the first time they’ve collected data like this outside of national parks.
Contrary to what some would believe, the map is not an aggregate of millions of sound recordings. In fact, it uses just over 600. But that’s still not enough sites to build a whole map. That’s where Mennitt comes in. He built a mathematical model to paint a portrait of soundscapes in between all of those points. The Natural Sounds and Night Skies map is not the product of millions of microphones, but of brushstrokes painted by a complicated formula.
The next step, as Mennitt said, is “so what?”
It’s a question that might be answered by researchers in all sorts of disciplines. While most work in some form of conservation or animal science, Kurt Fristrup said Harvard researchers are interested in using it to study the impacts of noise pollution on cardiovascular health in humans.
Of course, the map is also available to the public to use freely. Since it became available, Fristrup has referred to it when planning his own backpacking trips in the great outdoors.
“The more subtle effect of noise is that it masks other sounds. Sounds you otherwise might have heard are lost because the noise sort of smeared them out. For humans - for park visitors - that means you lose the potential to see some rare animal when you can’t hear the small sound that it happened to make. For wildlife, missing that sound is much more vital. Because these accidental sounds of nature are what sort of control predator prey interactions,” he said.
His team is also working on a map of light pollution in the United States - part of a larger collaboration with a team of Italian researchers mapping light pollution worldwide. Fristrup has planned trips using that map, too.
“I have specifically altered travel plans now to be in a particularly dark place to see a great night sky, and also to be in a particularly quiet place just to experience the sort of how big - this will sound odd - but how big solitude can be.”