RACHEL MARTIN, HOST:

Over the past decade, The National Park Service has placed hundreds of microphones around the country. These are some of the sounds those mics captured.

(SOUNDBITE OF WILDERNESS)

MARTIN: Coyotes in Colorado, a hummingbird in Washington State, elk from Sand Dunes National Park - but they weren't set up just to eavesdrop on wildlife. Last week, the Park Service's Division of Natural Sounds and Night Skies - yes, that is a real office. That division presented the results of their noise survey. It maps out the loudest and quietest corners of our country's National Parks. But the underlying purpose of the study is to draw attention to sounds that disrupt the peace and quiet we expect in these protected places. Imagine sitting in Golden Gate Park. You're there. You can smell eucalyptus trees. You are communing with nature when you hear this.

(SOUNDBITE OF EMERGENCY VEHICLE SIRENS)

MARTIN: Not so peaceful, right? Kurt Fristrup - he's one of the scientists behind the sound project. He says the noise we humans make in these spaces has consequences.

KURT FRISTRUP: And we now have wildlife research that shows that noise pollution can have significant impacts on animal densities and species diversities.

MARTIN: He says traffic noise, rumbling from a nearby factory, a helicopter buzzing the Grand Canyon - all of this creates a kind of acoustic fuzz that disrupts a whole environment.

FRISTRUP: And the problem with this chronic form of noise pollution is that it decreases the distance at which we could hear these interesting and subtle sounds of nature and also blurs their outline - much the way that fog would blur our ability to appreciate landscape scenery.

MARTIN: And it's not just that you won't be able to hear the birds singing. Fristrup says birds aren't able to hear one another or themselves. They might fly off course. And animals that are used to listening for their prey aren't able to catch their dinner. But he's quick to say this isn't just another depressing environment story.

FRISTRUP: The wonderful thing is that it's susceptible to immediate improvement.

MARTIN: After all, sound can be turned off.

FRISTRUP: This is one of the places where our society can not only dramatic improve the quality of life in our communities but also have tremendous benefits for the integrity of ecosystems and resources in National Parks.

MARTIN: Kurt Fristrup of The National Park Service. Transcript provided by NPR, Copyright NPR.