For the last 25 years scientists have been left baffled as to the cause of mysterious ocean noises that originate from the depths of the Pacific Ocean.
The strange sounds, known as the ‘Upsweep’, were first discovered in 1991. Scientists initially believed the sounds to be whale songs or ship vibrations, but these theories were quickly ruled out after further investigation.
The National Oceanic and Atmospheric Administration (NOAA) has described Upsweep as “a long train of narrow-band upsweeping sounds of several seconds duration each”.
The Upsweep you can hear in this extract is played at 20 times the normal speed.
The sound got louder until 1994 and has gradually subsided since, but can still be detected.
The NOAA believes it peaks in the spring and autumn.
Because of the large number ofvolcanoes in the Pacific, including submerged ones, volcanic activity is one suggested explanation.
Emile Okal of Northwestern University in Chica and Jacques Talandier, formerly with the French Atomic Energy Agency, hypothesised in 1996 it could be the sound of seawater contacting a large pool of hot lava.
Christopher Fox, director of NOAA’s acoustic monitoring project, said the movement of seawater can make noises like the movement of wind, so ocean currents may be responsible.
But overall, the NOAA still lists the origin of the mysterious noise as “unresolved”.
About 95% of our oceans remain unexplored, so more fanciful theories have included a sea monster, or undiscovered creature or geological process or other phenomena.
Never one to disappoint when an off-the-wall theory is needed, Scott C waring, editor of UFO Sightings Daily, said scientists were on the wrong track.
He speculated it only only stem from electrical equipment, and therefore aliens must have a secret underground base beneath the ocean.
But now a new theory has come forward…based on fish farting…seriously.
Simone Baumann-Pickering, a marine biologist at the Scripps Institution of Oceanography at the University of California, San Diego, said the sound starts after the sun sets,for a couple of hours, then stops and it happens again at dawn.
Biologists believe it could come from huge clouds of small fish and crustaceans which hide by day and come nearer the surface at night.
Scientist now believe the hum happens when fish are in a mesopelagic zone from about 660 feet under the to a depth of 3,300 feet.
One theory being looked at is a form of communication, whereas another is a more basic form of communication.
Ms Baumann-Pickering said: “It’s known that some fish are considered to be farting.
“That they emit gas as they change depths in the water column.
“The gas comes from a swim bladder inside the fish that controls its buoyancy.”
It seems further research is needed before the mystery is finally solved.