When a diver at the National Marine Mammal Foundation in California surfaced saying, "Who told me to get out?" the researchers there knew they had another example on their hands.
Once they identified NOC as the culprit, they made the first-ever recordings of the behaviour.
They found that vocal bursts averaged about three per second, with pauses reminiscent of human speech. Analysis of the recordings showed that the frequencies within them were spread out into "harmonics" in a way very unlike whales' normal vocalisations and more like those of humans.
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