Earth's mysterious hum captured for first time

For the first time in history, researchers have recorded the Earth's constant hum.
By Joseph Scalise | Dec 14, 2017
Scientists atthe Paris Institute of Earth Physics havefinally captured the Earth's mysterious hum, a discovery that could help researchers pin down the mechanisms behind the sound.

Our planet has many odd features. One of those is an eerie noise that, while constant, cannot be heard by humans. Researchers first detected the low-frequency signal -- which occurs separate of seismic activity -- in the mid 20th century, and the first study published on the noise came in 1998.

Since that time, many scientists have tried to record or capture the sound using land-based observations. Unfortunately, none of those proved to be successful. In the new study, the researchers finally captured the mysterious signal by measuring it deep under the ocean, according toInternational Business Times UK.

They did that by spending 11 months gathering data from 57 underwater seismometer stations. After eliminating all the ambient ocean signals, the team compared the remaining data with observations made by terrestrial stations and found they had a match.They also found that the Earth's hum is nearly 10,000 times below the threshold of human hearing, which begins at 20 hertz.

"A low noise level is needed to observe the small signal amplitude of the hum," the researchers wrote in the study, according to Newsweek. "At the ocean bottom, the noise level at long periods is generally much higher than at land stations."

While researchers are still not sure what causes the hum, they can now make strides towards figuring out what is behind the noise. Long-standing theories state it involves the constant pounding of waves on the ocean floor, while other research speculatesocean waves travelling along shorelines or under mountains could generate seismic activities that could be connected to the sound. The team hopes their findings will help figure out which theory is correct.

The recentstudyis published in Geophysical Research Letters.

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