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Despite the countless conspiracy theories surrounding a mysterious noise recorded in the Mariana Trench, researchers believe they have found the source.

The noise, notable for its extremely wide frequency range and 'metallic finale', likely represents the discovery of a new baleen whale call, according to the Oregon State University team that recorded and analysed it.


Scientists at OSU’s Hatfield Marine Science Centre have named the sound the “Western Pacific Biotwang (WPB).”

Between October 14 and November 6 2014, 326 of these WPB calls were recorded during 38 dives. Each of these calls were around five minutes apart and were recorded over long sequences. Further calls were recorded from March to April 2015, during which a total of 110 WPB calls were identified. Each of the calls were recorded using so-called "passive acoustic ocean gliders", which are unmanned vessels that can dive to depths of around 3,300 feet.

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Lasting between 2.5 and 3.5 seconds, the five-part call typically includes deep moans at frequencies as low as 38 hertz and a metallic finale that pushes as high as 8,000 hertz.

“It’s very distinct, with all these crazy parts,” said Sharon Nieukirk, senior faculty research assistant in marine bioacoustics at Oregon State. “The low-frequency moaning part is typical of baleen whales, and it’s that kind of twangy sound that makes it really unique. We don’t find many new baleen whale calls.”


Baleen whales are so called because they feed using baleen plates in their mouths to filter krill and small fish from seawater.

In particular, the researchers continued that the Western Pacific Biotwang most closely resembles the “Star Wars” sound produced by dwarf minke whales on the Great Barrier Reef. Minke whales are baleen whales and produce "regionally specific calls", which range from “boings” in the North Pacific to low-frequency pulse trains in the Atlantic.

“We don’t really know that much about minke whale distribution at low latitudes,” added Nieukirk. “The species is the smallest of the baleen whales, doesn’t spend much time at the surface, has an inconspicuous blow, and often lives in areas where high seas make sighting difficult. But they call frequently, making them good candidates for acoustic studies.”

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The Mariana Trench lies between Japan to the north and Australia to the south and features depths in excess of 36,000 feet and is the deepest known part of the Earth’s oceans.


Nieukirk said the Western Pacific Biotwang has enough similarities to the Star Wars call – complex structure, frequency sweep and metallic conclusion – that it’s reasonable to think a minke whale is responsible for it but there are still doubts.

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For example, baleen whale calls are often related to mating and heard mainly during the winter, yet the Western Pacific Biotwang was recorded throughout the year.

“If it’s a mating call, why are we getting it year round? That’s a mystery,” said Nieukirk. “We need to determine how often the call occurs in summer versus winter, and how widely this call is really distributed.”

The call is also difficult to identify when listening to other sounds recorded at great depths because of its vast frequency range.


“Now that we’ve published these data, we hope researchers can identify this call in past and future data, and ultimately we should be able to pin down the source of the sound,” Nieukirk concluded.

“More data are needed, including genetic, acoustic and visual identification of the source, to confirm the species and gain insight into how this sound is being used. Our hope is to mount an expedition to go out and do acoustic localisation, find the animals, get biopsy samples and find out exactly what’s making the sound. It really is an amazing, weird sound, and good science will explain it.”

The study is published in The Journal of Acoustical Society of America