The scientists harvested body parts from wild koalas that had been humanely euthanized for other reasons. When scientists looked at the voice boxes of male koalas, they found their vocal cords weren’t large enough to create the animals’ extremely low-pitched mating bellows. But further examination revealed a second, much larger pair of vocal folds located outside of the larynx, where the oral and nasal cavities connect.
Charlton and his colleagues used a combination of physical, video, and acoustic analyses to demonstrate that the newly discovered vocal folds outside of the larynx are capable of producing extremely low-pitched sound as the koala inhales air through its nostrils. (Read more about koalas in National Geographic magazine.)
It’s the first evidence in a land-dwelling mammal of an organ other than the larynx that is devoted to producing sound.
The only other example of a specialized sound-producing organ in mammals that is independent of the larynx is the phonic lips that toothed whales use to generate echolocation—or the natural sonar that helps them find prey, said Charlton, whose study is published in the journal Current Biology.
But Charlton and colleagues plan to keep looking to find other animals with such low voices.
here you can learn more and listen to a recording of the koalas