Oceans' waves may be source of Earth's hum, scientists say.(San Jose Knight Ridder Newspapers)

Byline: Glennda Chui

SAN JOSE, Calif. _ Scientists think they have found the source of a mysterious hum that reverberates through the Earth, too low for human ears to hear.

They used to think it came from earthquakes; a big quake will set the whole planet ringing like a bell. But even when there are no big quakes, the hum continues, a slow, steady slosh of waves around the planet.

Now, with instruments in California and Japan, scientists have pinpointed the source. The hum, they say, starts in the oceans, when winter storms whip the waves into a frenzy.

"These waves interact with each other to create longer waves that reach deep into ...