"Park Service Surveys The Environment's Accoustical Health"

The National Park Service has been documenting the acoustic environment in National Parks for years. But in addition to the sounds of nature --  Coyotes in Colorado, a hummingbird in Washington State, elk from Sand Dunes National Park -- the microphones also capture the sounds of civilization -- such as sirens.

Scientist Kurt Fristrup talks to NPR host Rachel Martin February 22, 2015.