Now, for the first time ever, scientists have captured Earth’s hum — its unique ‘song.’ They measured the constant humming from the Indian Ocean seafloor using special spherical Ocean-Bottom Seismometers (OCBs). The permanent drone, which has baffled scientists for a while now, comes from continuous vibrations too faint to be detected by the human ear.
From September 2012 to November 2013, the researchers deployed 57 of these OCBs, and measured several frequencies between 2.9 and 4.5 millihertz. That’s 10,000 times lower than the average human hearing threshold, the researchers noted in their study, published in the journal Geophysical Research Letters.
Attempts to measure the low-frequency drone had previously been attempted using seismometers based on land. Now, the new measurement taken from the ocean suggests that the humming occurs globally, which the researchers found by stripping data from other vibrations — like ocean currents, waves, seismic activity and glitches — from their recordings, and comparing the recorded hum with measurements taken by a land-based station in Algeria.
Combining the measurements taken from land seismometers and the new numbers from the OCBs, the researchers said that their findings can provide new insight into the mechanisms behind the Earth’s hum. Aside from this, their study could also help map the inside of the Earth with more detailed accuracy, the researchers pointed out. Earth is constantly in movement and they need to observe these movements, because the field could benefit from having more data, they concluded.
References: Livescience, Geophysical Research Letters, National Geographic, Washington Post