Except for the coast, the Western half of the U.S. appears relatively quiet. The quietest places in the U.S. are Yellowstone National Park in Wyoming and the Great Sand Dunes National Park in Colorado, which registered less than 20 decibels of background noise – comparable to what the U.S. would have sounded like before European colonization. The Eastern U.S. is another story. In most American cities, noise levels average 50 to 60 decibels, several orders of magnitude larger than the parks.
The National Park Service plans to use the map to identify places where human-made noise might be affecting wildlife, according to Science magazine. Animals such as bats and owls have far more sensitive hearing than humans, and man-made noise can easily drown out the natural sounds they need to hunt, researchers say.