Our Noisy Earth

Biophony is the word to describe what nature sounds like without any human made noise. There are few places on earth where this sound exists. We've populated and cultivated so much of the earth that we are permanently altering the way just about every ecosystem and habitat operates.
Anthrophony is man made noise.

Studies have been done that show that natural sounds fall into different frequencies so that many species can successfully live in the same habitat. For instance, different birds' calls are at different pitches, thereby allowing each type of bird to easily distinguish calls from its own kind. When man made noise enters the picture it disrupts the flow of things by causing animals not to be able to discriminate amongst animal sounds as easily. This can cause mating calls, predatory sound cues, and other important sounds to be missed or misinterpreted.

Sources:
Thompson, Clive. "Quiet Please!" Wired June 2008 pg. 66