A new study reveals the precise origin of the mysterious biotwang sound in the Pacific Ocean, first discovered near the Mariana Trench.
Researchers have finally pinpointed the source of this enigmatic noise to the world’s deepest ocean trench. The strange sound, referred to as “biotwang”, is actually the call of the Bryde’s whale (Balaenoptera edeni). This whale species uses its calls to locate its peers. Scientists first detected the unusual noise in 2014 while using underwater gliders to conduct acoustic surveys of the Mariana Trench. This trench is the deepest oceanic trench on Earth, extending over 2,400 km south of Japan and reaching a maximum depth of 10,935 m, according to Live Science.
Bryde’s whale hunting sardines underwater. (Photo: Scuba Magazine).
The biotwang sound can be divided into two distinct parts: the first is a low, rumbling sound that resonates in the deep water layers, and the second is a metallic sound with a pitch that researchers liken to noises from spaceships in films like Star Trek and Star Wars. These sounds initially puzzled scientists. However, in 2016, a research group speculated that biotwang was likely the call of large baleen whales, such as the blue whale (Balaenoptera musculus) or the humpback whale (Megaptera novaeangliae). Nonetheless, the sound did not match the calls of any known whale species.
In a newly published study on September 18 in the journal Frontiers in Marine Science, researchers were finally able to demonstrate that the Bryde’s whale produces the noise, partly thanks to a new artificial intelligence (AI) tool that helped sift through over 200,000 hours of recordings, which contained various sounds from the ocean. The research team suspected that Bryde’s whales were behind the biotwang when they observed ten whales swimming near the Mariana Islands and recorded nine of them producing the characteristic noise.
“One or two times could be coincidence, but nine times clearly points to the Bryde’s whale,” said lead researcher Ann Allen, a marine biologist at the Pacific Islands Fisheries Science Center of the National Oceanic and Atmospheric Administration (NOAA).
To confirm that Bryde’s whales were making the calls, the research team compared the noise with the migration patterns of the species, classifying recordings collected over several years by monitoring stations across the Mariana Islands and the surrounding area. They accelerated the process by using AI to transform biotwang into images, known as spectrograms, making it easier to distinguish various noises through machine learning algorithms.
The study also found that biotwang could only be heard in the northwest Pacific, even though Bryde’s whales inhabit a broader area, suggesting that only a specific population of whales produces the sound. Data also revealed a spike in biotwang in 2016, coinciding with rising ocean temperatures due to the El Niño phenomenon, which increased the number of Bryde’s whales passing through the area. Researchers are still unclear as to why the calls sound so peculiar. They will need more data to reach definitive conclusions.
