The Mariana Trench is one of the most mysterious places on Earth. The trench is nearly seven miles (about 37,000 feet) deep and is located on the bottom of the Pacific Ocean, making it difficult to reach, so only a few people have dived to explore.
So it was no surprise that when anomalous noises from the Mariana Trench were first recorded in 2014, fears of an alien invasion were triggered.
These sounds last between 2.5 and 3.5 seconds and are known as "biobounces", but their source remains unknown.
Ten years later, scientists from the National Oceanic and Atmospheric Administration (NOAA) in United States reanalyzed the voices and believe they have finally uncovered the truth. These eerie sounds were first recorded in 2014 by underwater gliders that were used to conduct acoustic surveys of the trench.
The sound lasts between 2.5 and 3.5 seconds and contains five parts, including a deep moan with frequencies as low as 38 Hz, and an epilogue up to 8,000 Hz. The researchers were initially puzzled by the sounds.
However, in 2016, a team from Oregon State University (OSU) suggested that this could be a new type of baleen whale chirp that had not been heard before. Sharon Nieukirk, · Sharon, a senior research associate in marine bioacoustics at the university, said at the time: "It's very unique with these peculiar parts. Low-frequency moaning sounds are typical of baleen whales, and that whiskering sound makes it very distinctive. We have not found many new baleen whale calls. ”
Now, scientists have reanalyzed these sounds using a combination of visual and acoustic survey data, and the results show that the OSU team's speculation is not unfounded.
New research suggests that the source of the biological bouncing is not baleen whales, but Bryde's whales. In the study published in the journal Frontiers in Marine Science, Dr. · Allen Ann. Ann Allen's team explained: "It was initially thought it was sent by baleen whales, but the species could not be identified without visual verification. By analyzing visual and acoustic survey data collected in the Mariana Islands, we determined that the biobouncing was emitted by Bryde's whales. ”
Bryde's whales are widely distributed in warm tropical and temperate oceans, including the Atlantic, India and Pacific Oceans. Researchers observed ten Bryde's whales in the area and recorded nine whales emitting this unique sound.
However, to prove that these whales were indeed the source of the sound, the team turned to artificial intelligence. "We used a combination of manual and machine learning annotation methods to detect the identification of bio-bouncing in the extensive historical passive acoustic monitoring data we collected," they explained in the study. "We have identified seasonal occurrences of biobounces in the Mariana Islands and Wake Island in the east, with occasional occurrences in the Northwest Hawaiian Islands and near the equator (Holland Island)."
The team still doesn't know why these whales' calls are so unique, or why they make these sounds.
However, in an interview with Popular Science, Dr. Allen suggested: "They may use biobounces as a kind of linkage cry, similar to the 'Marco · Polo' in the ocean." ”
"But we need more information to know for sure."