Eavesdrop on Mother Earth (you'll need to turn up the volume):
Courtesy Terry Averkamp/ Department of Physics and Astronomy/Univ. of Iowa
Listen: Hear the Earth Hum
The earth hums, emitting a tone too low for human ears to detect. Geophysicists have finally located the source of the noise. As they report in this week's issue of the journal Nature, it comes from the globe's largest oceans during winter, apparently the result of powerful winter storms. NPR's David Kestenbaum reports.