Mystery of deep sea ‘biotwang’ sounds finally solved

Mystery of deep sea ‘biotwang’ sounds finally solved

Melissa Hobson

It was about a decade ago that the inexplicable sound first blared from computer speakers — a low, booming rumble recorded by microphones buried deep in the ocean, followed by a squealing, mechanical echo like a frog burping in space — and perplexed researchers dubbed it the “biotwang.”

“There’s a low-frequency part that sounds like a groan,” says Lauren Harrell, a data scientist at Google Research’s AI for Social Good, adding her own impression of a hearty groan, “and then there’s a high-frequency component that sounds to me like the original sound. Star Trek It’s the “bip-boom, bip-boom” sound of the Enterprise.

In 2014, an autonomous underwater glider recorded the strange sounds echoing miles deep in the Mariana Trench for the first time. Researchers were unable to identify the source of the sounds, but they have some hypotheses: “There are many other man-made sounds. Star Wars“We speculated that this whale’s call was a baleen whale’s call because it was similar to what acoustic whales make,” says Anne Allen, a research oceanographer at the National Oceanic and Atmospheric Administration (NOAA). But, she points out, “someone who isn’t familiar with whales would never guess that this is an animal sound.”

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Listen to the bio twang for yourself:

But identifying which marine animal is making the strange noises isn’t easy, since someone on board needs to see and identify the source at exactly the same time that the sound is heard. “This takes a lot of time, effort, and a lot of luck,” Allen says.

Thus Allen, Harrell and their colleagues finally solved the mystery of biotwang. While studying whales in the Mariana Islands archipelago near the Mariana Trench in the North Pacific Ocean, Allen and other NOAA researchers discovered a mysterious species called Bryde’s whale (Balaenoptera edenii) 10 times. Bryde’s whales are widely distributed across the vast open ocean, making them difficult for scientists to observe and study. Of the nine times a Bryde’s whale showed up, the researchers also heard a biotong. “Once it’s a coincidence,” Allen says. “Two times it’s a coincidence. Nine times it’s definitely a Bryde’s whale.”

After identifying the source, the researchers combed through years’ worth of audio data from underwater hydrophones to see where this particular whale had been heard before. But NOAA’s ever-growing database contains more than 200,000 hours of such recordings. “The amount of data is just too much to analyze (by hand),” said Olaf Meineke, a researcher at Griffith University in Australia who specializes in baleen whales and is not involved in Allen’s new biotwang study, said Wednesday. The forefront of marine science.

While analyzing audio data for another project, Allen was “astonished” by the sheer volume of data he had to analyze. At one point, his father suggested he “just ask Google.” So Allen reached out to the company’s staff, and to his surprise, they agreed. The company offered an AI tool that would speed up analysis by converting audio data into images called spectrograms and using image recognition to train algorithms to look for specific frequencies.

A new study provides evidence that biotwangs are associated with Bryde’s whales in the western North Pacific. The data confirmed that the animals the researchers studied constitute a unique Bryde’s whale population and showed where they were found in the ocean during different seasons and years. This was previously not possible because scientists could not distinguish between different populations of the cryptic whale. And when a strong El Niño shifted the location of the whales’ food (mainly krill, sardines, and anchovies) in 2016, biotwangs were seen in abundance, even in the Northwestern Hawaiian Islands, where these whales only venture under certain climatic conditions. This may mean that the whales’ movements are at least partly determined by the distribution of prey, which changes with environmental conditions.

“We seem to be too disconnected from this incredible underwater acoustic world, or at least have no access to it at all. I think it’s time to change that.” Olaf Meineke, Griffith University

If scientists can know when and where these whales migrate, Harrell says, AI models can “link that data to climate and environmental factors” to help with conservation efforts. As climate change worsens and there are likely changes to El Niño and its cold-water counterpart, La Niña, “these whales might have to migrate farther away and work a little harder to find food,” Allen says.

The technology isn’t perfect: “These algorithms can only search for known frequencies,” Meineke says. Baleen whale songs change over time and between populations. But the tool is open source, so other scientists can use it to learn more about whale language. “We seem to be too disconnected from, or completely inaccessible to, this incredible acoustic underwater world,” Meineke says. “I think it’s time to change that.”