Vocal fry—or speaking in a creaky, lower register—can be a divisive topic for those living in the United States. Some find the sound abrasive or unprofessional, while others view such criticism as tasteless.
But now, new research shows that humans aren’t the only species that can produce this guttural vibration—dolphins and other toothed whales routinely use an air-driven nasal sound akin to vocal fry, and it’s critical to their survival.
In a study published last week in Science, researchers uncovered that these animals use structures in their noses called phonic lips—which vibrate like the larynx does in humans—to produce the sound. The animals use vocal fry in echolocation clicks for hunting.
“Vocal fry is a normal voice register that is often used in American English. Kim Kardashian, Katy Perry and Scarlet Johannsen are well-known people using this register,” co-author Coen Elemans, a voice scientist at the University of Southern Denmark, says in a statement. “During vocal fry, the vocal folds are only open for a very short time, and therefore it takes very little breathing air.”
To figure out how the animals were making this noise, Elemans and his colleagues inserted endoscopes into the blowholes of trained dolphins and porpoises to film their phonic lips in action. They also filmed wild whales with small sound-recording tags and examined deceased whales.
“We showed that there’s definitely movement of these [phonic lips] while they make echolocation clicks,” Elemans tells NPR’s Ari Daniel.
The researchers found the location of the phonic lips is also crucial. When whales dive deeper than about 330 feet, their lungs collapse due to the pressure. However, air remains in the skull’s nasal passages. Because vocal fry requires little air, it works well for echolocation. These deep-diving mammals repeatedly move air back and forth through their nose, vibrating the phonic lips.
“They basically push [air] one way and then recycle it and push it back without breathing,” Elemans says to New Scientist’s Corryn Wetzel. “By doing that, they can make the loudest sound of any animal on Earth by far.”
The study shows that toothed whales have three vocal registers, just like humans: normal chest voice (which we use to speak), falsetto (which we use for singing) and a vocal fry. Prior to this, the use of vocal registers had only been confirmed in humans and crows, per a statement. Toothed whales use their phonic lips to produce sounds in all registers. But the chest and falsetto registers are used for communication, while vocal fry is for navigation and hunting.
The research calls attention to some of the similarities in the way that humans and toothed whales vocalize, researchers say.
“They show, to some extent, that the physical mechanism is the same as the one we use,” Andrea Ravignani, a comparative bioacoustician at Aarhus University in Denmark and the Max Planck Institute for Psycholinguistics in the Netherlands who was not involved in the study, says to the Washington Post’s Dino Grandoni. “The finding is quite unexpected and mind-blowing.”