It might sound like something plucked from a science fiction novel, but there is apparently a mysterious hum emanating from the Earth itself.
Experts from around Europe report in the Journal of Geophysical Research Letters that they have managed to record the natural hum of the planet which has eluded them for decades.
The existence of the hum has been known since 1959, but it wasn't until 1998 that scientists could actually prove that it was real.
Attempts to record the sound have been attempted in the past but they failed because they were all made on land. The trick to capturing the elusive readings was to head to the ocean floor.
Researchers from Britain, France and Germany studied 11-months of recordings made on the floor of the Indian Ocean, east of Madagascar, a patch which covers around 1,2000 square miles.
The data was collected between 2012 and 2013, but it was only after experts filtered out interfering sounds from sea waves and electronics on two specific sites that they were finally able to hear the Earth's native sound.
Despite this, it is still virtually undetectable to the human ear, as it the sound doesn't exceed 4.5 millihertz; a frequency that is 10,000 times lower than what humans can hear.
With this new knowledge, we are sadly no closer to learning what the hum is and what causes it.
The most common theory is that it is caused by the ocean's waves, but others have suggested it could stem from storms or turbulence in the atmosphere.
Spahr Webb of Colombia University's Earth Institute, who was not part of this research, is one expert who reasons that waves are responsible for the sound:
He is quoted by National Geographic as saying:
Fairly early on, people realised this was caused by ocean waves
As instruments have gotten better, we've realised the hum's going on all the time.
Turbulence in the atmosphere is moving very, very slowly. It's not energetic enough.
The hum is solely associated with ocean waves.
The hum will help scientists learn more about the interior of the Earth, something which they can only currently do during an earthquake.
The constant hum gives out a signal which can be detected all over the globe, making it possible to conduct further research of this kind.
That can be used to map the structure of the Earth.
Getting data from new places is going to help.
HT Uni Lad