A drone picked up the eerie 3.5-second-long noise deep in the Pacific Ocean’s Marianas Trench Marine National Monument (whose lowest points sit nearly seven miles below the ocean’s surface) multiple times between autumn 2014 and spring 2015.
Now, according to a new study in The Journal of the Acoustical Society of America, researchers are saying that the mysterious sound is an unknown baleen whale call.
Nobody is quite sure what this new whale call — nicknamed the Western Pacific Biotwang — is communicating, but you can hear it for yourself below:
“It’s very distinct, with all these crazy parts,” said Sharon Nieukirk, one of the study’s researchers, in a news release. “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.”
But before determining that the sound in question was in fact a baleen whale call, Nieukirk and her team were stumped. They first searched for possible human or geological origins for the sound, but came up short.
That’s when they turned to a call from a minke whale, nicknamed “Star Wars” and recorded in 2001 around Australia’s Great Barrier Reef.
After comparing the frequency and structure of the “Star Wars” call and their new call, the researchers concluded the Western Pacific Biotwang sound likely came from a similar type of animal (dwarf minke whales are in fact a subspecies of baleen whales).
The research team now says that they’re looking forward to returning to the Marianas Trench in hopes of actually finding the animal responsible for making the Western Pacific Biotwang sound, and figuring out exactly how and why it’s doing it.