© Getty ImagesResearchers have identified Bryde's whales as the origin of the mysterious "biotwang" noises. In this photo, a Bryde's whale lunges through a school of fish.
Scientists first detected the unusual noises in 2014 while using underwater gliders to carry out an acoustic survey of the Mariana Trench — the world's deepest ocean trench, which spans more than 1,500 miles (2,400 kilometers) south of Japan and has a maximum depth of 35,876 feet (10,935 meters).
The biotwang sound can be broken down into two distinct parts: first, a low, grumbly sound that reverberates through the deep; and second, a high-pitched, metallic ringing that researchers have likened to the sounds made by spaceships in Star Trek and Star Wars.
The sounds initially stumped scientists. But in 2016, researchers revealed that biotwang was most likely a call from large baleen whales, such as blue whales (Balaenoptera musculus) or humpback whales (Megaptera novaeangliae). However, the sounds did not match any known whale calls.
In the new study, published Wednesday (Sept. 18) in the journal Frontiers in Marine Science, researchers were finally able to prove that Bryde's whales were making the noises, thanks in part to new artificial intelligence (AI) tools that sifted through over 200,000 hours of audio recordings containing various ocean sounds.
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