All right, folks. We’ve had our warnings, and now it really is time to keep it down. Experts say anthropogenic (human-made) noise is drowning out natural silence and sounds in the majority of protected areas in the United States. They published their research in the journal Science.

A babbling brook or a forest full of birdsong may soothe a stressed-out human, but for the plants and animals that live there, every single sound serves a function. Studies have shown that noise pollution can mess up animals’ migration paths, stop them from mating, and lead them to make fatally bad decisions.

Parks, wilderness, and other protected areas currently make up 14 percent of our country’s landmass. But as urbanization continues, spillover from human settlement draws nearer to every open space; 80 percent of the country is within .6 miles of a road and its accompanying traffic.

To find out how far our racket has reached, researchers captured audio recordings at 492 spots across the U.S.—some protected, some not—and used computer modeling to estimate natural sound levels at each location.

The results were not encouraging. The researchers say our noise pollution doubled noise levels in more than half of protected areas. In about one-fifth of those areas, noise was increased tenfold—an increase that shrinks the audible range of a bird’s call to 10 percent of its natural reach.

Median noise exceedance—the amount that anthropogenic noise increases sound levels above the natural level—in protected area units across the contiguous United States. R.T. Buxton et al., Science (2017)

“We were surprised we found such high levels of noise pollution in such high amounts of protected areas,” lead author Rachel Buxton of Colorado State University (CSU) told Science.

This is bad for people, too. Counterintuitive though it may sound, tourism plays an integral role in the success of national parks and other protected spaces. But an escape to nature loses some of its appeal if all you can hear are trucks and machinery.

Senior author George Wittemyer, also of CSU, said that while these findings are troubling, it’s important to remember that the worst is not inevitable.

“Numerous noise mitigation strategies have been successfully developed and implemented,” he said in a statement. “Our work provides information to facilitate such efforts in respect to protected areas where natural sounds are integral.”

"Next time you go for a walk in the woods, pay attention to the sounds you hear—the flow of a river, wind through the trees, singing birds, bugling elk,” Buxton added. “These acoustic resources are just as magnificent as visual ones, and deserve our protection.”