New research suggests that traffic noise (apart from pollution and general hectic motion) degrades the natural habitat of songbirds, and perhaps other animals. Boise State University biologists created a "phantom road" using speakers to create traffic noise in a natural, roadless songbird habitat.
From the abstract of their scientific paper in PNAS:
Thirty-one percent of the bird community avoided the phantom road. For individuals that stayed despite the noise, overall body condition decreased by a full SD and some species showed a change in ability to gain body condition when exposed to traffic noise during migratory stopover. We conducted complementary laboratory experiments that implicate foraging-vigilance behavior as one mechanism driving this pattern.