Using specialized instruments, scientists measured the continuous low-frequency drone the Earth is known to produce. Supposedly, these come from the planet's vibrations, but the exact mechanism behind the sound is still to be identified.
A Humming Planet
Like a permanent undertone to the dissonance of busy urban centers or nature’s own harmonious melodies, the Earth itself hums a low-frequency tune. The permanent drone, which has baffled scientists for a while now, comes from continuous vibrations too faint to be detected without a specialized instrument.
Now, for the first time ever, scientists have captured Earth’s hum — its “song,” if you will. They measured the constant humming from from the Indian Ocean seafloor using special spherical Ocean-Bottom Seismometers (OCBs).
“It’s like taking a piano and slamming all the keys at the same time,” Spahr Webb, a professor at Columbia’s Lamont-Doherty Earth Observatory not associated with the study, told National Geographic. “Except they’re not nice harmonics. They’re oddball frequencies.”