Scientists have studied the complex vocalisations of whales since the discovery of evocative songs sung by humpback whales in the 1960s.
Female sperm whales communicate using a series of clicks that researchers call "codas". The Cetacean Translation Initiative (CETI), which studies sperm whales in the Caribbean, has found that these codas share a strikingly human-like feature: they resemble vowels. In human linguistics, vowels are characterised by the free flow of air through a vibrating vocal tract; their fundamental acoustic frequency (F0) is determined by sex and body size, while "formants" (F1, F2, F3 and so on)—concentrations of sonic energy at specific higher frequencies shaped by the arrangement of tongue and lips—determine which specific vowel is heard.
To human ears, sperm-whale clicks are too infrequent and irregular to sound like pitches. But when researchers removed the silences in software, they could treat the clicks as pitches and examine their spectral properties. Using an AI system trained to learn human language, Gasper Begus, a linguist at the University of California, Berkeley and the study's lead author, found that the codas include two spectral patterns resembling human F1 and F2 formants, albeit at much lower frequencies. The patterns were discrete rather than continuous, suggesting the whales intended them to be distinct—just as human vowels are. The researchers dubbed them the a-coda and i-coda vowels. The whales also produce diphthongs, two vowels gliding quickly from one to another, like the "ah-ee" sound in English words such as "ride". These results were published in Open Mind.
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