At the height of the Cold War during the 1960s the U.S. Navy established something known as SOSUS (short for Sound Surveillance System), a network of hydrophones (that is underwater microphones) designed to track the movement of Soviet submarines. SOSUS used hydrophones set hundreds of yards below the ocean surface, at the depth at which sound waves become trapped in a layer of water known as the 'deep sound channel', where the combination of temperature and pressure cause sound waves to continue travelling without being scattered by the ocean surface or bottom.

The US Navy has become rather less interested in tracking submarines and since 1991 the SOSUS network has been used by the U.S. National Oceanic and Atmospheric Administration for its Acoustic Monitoring Project as part of the VENTS Program. VENTS is concerned with research into submarine volcanic activity and so the Acoustic Monitoring Project is basically using SOSUS to listen in on the 'deep sound channel' to pick up the sounds of any such activity.

Naturally whilst the scientists employed on the project are busy listening out for underwater volcanoes and suchlike they are picking up all kinds of sounds including those made by various whale species, ocean currents, ice movements as well as ships and submarines.

Many of these sounds are distinct and easily-identifiable as Christopher Fox of the NOAA was quoted as saying;

The sound waves are almost like voice prints. You're able to look at the characteristics of the sound and say: 'There's a blue whale, there's a fin whale, there's a boat, there's a humpback whale and here comes an earthquake'
And when they came across a sound they couldn't easily identify they amused themselves by giving the unidentified sound a name such as 'Train', 'Whistle', 'Slowdown', 'Upsweep' and 'Gregorian Chant'. ('Upsweep' for example, has now been identified as a previously unknown undersea South Pacific volcano.)

And then in 1997, they heard a new noise that they hadn't heard before, and they called it 'Bloop'.

Bloop sounded like a whale, but since the sound had been picked up simultaneously by two hydrophones over 3,000 miles apart, they knew that it was a much louder noise than any known whale could produce. In fact the noise is louder than any recognized animal noise known on Earth.

They were convinced that Bloop was definitely biological in origin and was suggested that it might be some kind of large squid, but unfortunately cephalopods are not biologically equipped to make that kind of noise, so it is unlikely to be a squid whether giant or colossal.

It's something else. It's very big and it lives somewhere in the deep dark depths of the ocean. And it goes bloop.


Bloop can be heard at http://www.pmel.noaa.gov/vents/acoustics/sounds/bloop.wav

The official description of the sound goes thus;

This sound was repeatedly recorded during summer, 1997 on the Equatorial Pacific Ocean autonomous hydrophone array. The sound rises rapidly in frequency over about one minute and was of sufficient amplitude to be heard on multiple sensors, at a range of over 5,000 km. It yields a general location near 50oS; 100oW. The origin of the sound is unknown.

SOURCES

VENTS program website at http://www.pmel.noaa.gov/vents/

Tuning in to a deep sea monster (June 13, 2002) at http://www.cnn.com/2002/TECH/science/06/13/bloop/

Mystery Underwater Noise Could Be Unknown Monster (Story originally published by: The Sydney Morning Herald / Australia - June 13.02) From the FarShores CryptoNews website at http://www.100megsfree4.com/farshores/cmon021.htm