Sub-sonic hum from depth of Earth puzzles scientists

The vibrations made by the Earth cannot be heard by the humans, as our lower hearing threshold is 20 Hertz.

NASA Earth

The planet in which we live, the Earth is a storehouse of surprises, mysteries, and miracles which are beyond explanation. Now, a new study has captured unknown hums coming from deep inside the Earth. Even though the sound has been recorded, scientists involved in the research are not sure about the origin.

An unsolved mystery

It has long been speculated that Earth constantly generates low-frequency vibrations from its depth. In 1959, researchers made the first attempt to detect this hum, but it took more than 39 years for the scientists to prove its existence. Researchers confirmed in 1998 that a mysterious hum is coming from the deep infinity of Earth.

Since 1998, more than hundreds of efforts were made to record this hum, but all these attempts were made using seismometers on land. In the new study, researchers have captured the hum from deep inside the ocean, which is undoubtedly a milestone achievement.

Details of the study

The research team was led by Martha Deen at the Paris Institute of Earth Physics. In the initial phase of the research, the team captured data from 57 seismometer stations located in the Indian Ocean and the east of Madagascar.

"We demonstrate the presence of eigenmodes at two ocean bottom seismometers for the first time. We do so by noise reduction and calculation of the auto-correlation of the seismograms. We successfully removed electronic glitches of varying periodicity from vertical OBS data, which reduced the noise level by 28 dB," wrote Martha in the study report.

Further analysis of the data helped the researchers to reach a conclusion that the natural vibration of Earth peaks at various frequencies between 2.9 and 4.5 millihertz.

Interestingly, the vibrations made by the Earth cannot be heard by the humans, as our lower hearing threshold is 20 Hertz. As the hum has been recorded from the surface of the ocean, scientists believe that this hum will be present all across the globe, as more than 70 percent of our entire planet is covered with water.

Martha Deen and the researchers involved in the study believe that the data obtained from the study can be used to map the interior of the Earth with more precision and accuracy.