How dolphins, porpoises, killer whales, sperm whales and other toothed whales make their range of sounds has been a mystery — until now.
Everything is in the nose, the researchers found.
The animals emit loud clicks for echolocation—the process of locating prey by sound waves—as well as softer pulses and whistles for communication.
Scientists say the sound is produced by an air-driven system in the nose, similar to the human vocal cords.
The study, published in the journal Science, also suggests that the air-powered sound waves are a way for toothed whales to find food in deep water.
Loudest voice in the animal kingdom
“Echolocating toothed whales make the loudest sounds in the animal kingdom by forcing high-pressure air through structures in their noses called articulatory lips,” said Peter Madsen, professor of sensory physiology at Denmark’s Aarhus University and an expert in whale biology. .
The articulating lips are open for about a millisecond, and when they “flap together, they create a tissue vibration that creates a very loud click in the water in front of the whale, which is used to echolocate prey to depths of more than 1,000 meters,” said Professor Madsen. “
The articulating lips are composed of connective tissue and fat.
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Research has shown that the resulting sound operates in a different vocal range than the human voice.
The scientists say it’s a fry register for clicks, a chest register for bursts and a falsetto register for whistles.
For humans, the fry register represents the lowest pitch, the chest register represents normal speaking voices, and the falsetto register represents higher frequencies.
Coen Elemans, a professor of bioacoustics at the University of Southern Denmark who co-led the study, said the sounds were said to be produced “by the same mechanism, self-sustained oscillations induced by airflow”.
“But the key difference is that in humans and other land mammals, air is used both as a propellant for vibrating the vocal cords and as a medium for sound transmission,” he added.
Whales evolve a whole new set of sound sources
Researchers used recording tags of sperm whales, false killer whales and bottlenose dolphins to study sound production in the wild.
They used video from an endoscope (a thin, tube-like instrument) to film the articulating lips of captive and bottlenose dolphins. They also studied the vocal lip surgery and anatomy of stranded dolphins.
“During evolution, toothed whales lost their vocal cords, but evolved a whole new set of sound sources in their noses,” added Professor Madsen.