A team of oceanographers and marine biologists from the NOAA Pacific Islands Fisheries Science Center and Oregon State University has identified a mysterious noise heard in the Pacific Ocean for two decades as the sounds of Bryde's whales.

In their study published in the journal Frontiers in Marine Science, the group identified the sound and worked with a team at Google to develop an AI application that could be used to track the whales' movements.

The mysterious sound was first recorded in 2014, when its metallic ping was designated a "biotwang." Since then, the sound has been recorded multiple times in multiple locations. In 2016, a team at Oregon State University found evidence that it was most likely some type of baleen whale.

In this new effort, the research team found that the earlier finding was correct—the sound is emitted by Bryde's whales.

The research team was able to make the connection while surveying whales around the Mariana Islands, where they spotted several of the seldom-seen whales. As they continued their survey, they lowered microphones into the water and recorded the mysterious biotwangs simultaneously with nine more Bryde's whales' sightings, confirming that they were the source.

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