Creepy sounds are echoing through Mariana Trench, and we now know the cause

Mysterious noises have been coming from the Mariana Trench, the deepest ocean trench, since 2014. Scientists now finally know the reason behind them. Described as "biotwang" noises, they sound like something emanating from sci-fi starships. However, they are simply whale calls being made by Bryde's whales, as per a new study published in the journal Frontiers in Marine Science.

Researchers say the whales use the calls to locate one another like a giant game of Marco Polo.

"It's possible that they use the biotwang as a contact call, a sort of 'Marco Polo' of the ocean," study lead author Ann Allen, an oceanographer at the National Oceanographic and Atmospheric Administration's (NOAA) Pacific Islands Fisheries Science Center, told Popular Science.

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In 2014, when scientists were carrying out an acoustic survey of the Mariana Trench using underwater gliders, they noticed some strange noises coming from the region. Notably, the deepest trench in the world spans more than 1,500 miles (2,400 kilometres) south of Japan and has a maximum depth of 35,876 feet (10,935 metres).

The whales were making two types of biotwang noises which initially stumped scientists who tried to figure out their source. First was a low, grumbly sound that reverberated through the deep.

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The second one was a high-pitched, metallic ringing, something researchers say was similar to the noise made by spaceships in Star Trek and Star Wars.

In 2016, large baleen whales, such as blue whales or humpback whales were thought to be the source of the biotwang. However, the sounds did not match any known whale calls.

Bryde's whales confirmed as source of sounds

But the latest study published on September18 confirms that the sounds were being made by Bryde's whales. This was deduced after new artificial intelligence (AI) tools went through over 200,000 hours of audio recordings containing various ocean sounds.

Another interesting thing the study found was that the biotwang was heard only in the northwest Pacific. Bryde's whales are not confined to this region, which suggests that only a specific population of the whales is making the noise.

Bryde's whales were circled in as the suspect when 10 of them were spotted swimming near the Mariana Islands. They recorded nine of them making the distinctive noise.

"Once, it's a coincidence. Twice is happenstance. Nine times, it's definitely a Bryde's whale," Allen told Scientific American.

To be fully sure, the team matched the occurrence of the noises to the migration patterns of the whales. AI was used to check through audio recordings captured by monitoring stations across the Mariana Archipelago and nearby areas over the past many years.