Bill McQuay

Every place has its own sound. A small group of scientists is hard at work recording the natural sounds of national parks all across the U.S. — more than 70 soundscapes so far.

For our series on the centennial of the national parks, we traveled to Colorado, to find out how they create these portraits of sound.

First Lesson: It's Very Hard To Escape The Sound Of Humans.

Acoustic biologists who have learned to tune their ears to the sounds of life know there's a lot more to animal communication than just, "Hey, here I am!" or "I need a mate."

From insects to elephants to people, we animals all use sound to function and converse in social groups — especially when the environment is dark, or underwater or heavily forested.

The natural world is abuzz with the sound of animals communicating — crickets, birds, even grunting fish. But scientists learning to decode these sounds say the secret signals of African elephants — their deepest rumblings — are among the most intriguing calls any animal makes.