Scientists finally found answer to what the 'most mysterious underwater sound' is after more than 20 years

Scientists have finally uncovered what the decades-old ‘mysterious rumble’ from underwater is.

For over 20 years, experts have been researching to work out what the strange noise was that was recorded in 1997 from under water.

At the time it was heard, researchers were listening for underwater volcanic activity, but instead stumbled across a strange and very loud sound…that appeared to have no explanation.

Using hydrophones, which are basically underwater microphones, placed more than 3,219km apart across the pacific, they captured multiple hearings of the sound.

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It was unheard of, and had characteristics that scientists were just baffled by.

The sound became known as the ‘bloop’.

Since 95% of the ocean is undiscovered, theories ran wild.

Scientists' suggestions included secret underwater military exercises, ship engines, fishing boat winches, giant squids, whales, or an undiscovered sea creature that biology had yet to uncover.

Over the last 20 years, hydrophones have been spread even closer to Antarctica in an ongoing attempt to study the sounds of seafloor volcanoes and earthquakes.

It was during these efforts, that they discovered the origin of the ‘bloop’!

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It was on earth’s lonely southernmost land mass that researchers pinpointed that the noise was the sound of an icequake.

What exactly is an icequake, you may ask?

It is the cracking and breaking of an iceberg moving away from an Antarctic glacier. Pretty cool, right!

This seems to be as a result of global warming, with more and more icequakes occurring annually and eventually melting into the ocean.

The National Ocean Service’s website says: “PMEL’s Acoustics Program develops unique acoustics tools and technologies to acquire long-term data sets of the global ocean acoustics environment, and to identify and assess acoustic impacts from human activities and natural processes on the marine environment.”

But this isn’t the only strange noise that scientists are working to uncover under the sea.

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The ‘boing’ was another mystery sound that was originally heard in the 1950s.

Despite receiving public attention for years after, the Southwest Fisheries Science Center acoustics team followed the sound in 2002, and identified its source as minke whales offshore the Hawaiian Islands.

Another peculiar sound known as the ‘slow down’ was recorded in 1997, which was clearly the year of strange underwater noises!

It was likened to a distant wailing or something falling from the sky, and researchers believe that it may be an iceberg that has hit the seafloor and has slowed to a halt.