Scientists have captured a noise from deep inside the Earth, however, they are still no closer to working out what it is.
The authors of the research explained, “the Earth’s hum can be used to study the Earth’s deep interior.”
They have been trying to record the elusive sound since 1959, but it was not until 1998 that its existence was finally proved.
The Earth is constantly expanding and contracting, which creates a sound that is inaudible to human ears.
The frequency of the hum is approximately 10,000 times smaller than the lower hearing threshold of the human ear (20 hertz).
Scientists wrote in a recent study, published in Geophysical Research Letters: “Station coverage in the oceans is much sparser than on land, leaving great parts of the Earth uncovered.”
Now, researchers have captured the hum for the first time using seismic instruments at the bottom of the ocean.
The researchers first collected data from 57 seismometer stations in the Indian Ocean, between 2012 and 2013.
They then applied a combination of techniques to remove interference from ocean infragravity waves, currents and electronic glitches, and corrected for the signal generated by any earthquakes.
Back in 1998, Japanese scientists successfully proved the sound was real, however, it has never been recorded in the depth of the ocean before.
Geophysicists used sophisticated “ocean bottom seismometers” to capture and isolate the Earth’s hum, however, due to the sound of the ocean itself, it made it hard to hear the Earth.
The researchers wrote: “A low noise level is needed to observe the small signal amplitude of the hum.
“At the ocean bottom, the noise level at long periods is generally much higher than at land stations.”
The team of researchers used sophisticated mathematical techniques to remove the sound of ocean currents and electronic glitches.
This breakthrough can help improve our understanding of Earth itself.
By analysing the sound of the planet, scientists might one day understand what is really happening beneath the surface.