Elephants are communicating using infrasound in a very similar manner to human speech or singing, new research has revealed.
The sounds, which are are as low as the lowest notes of a pipe organ, can be heard by other elephants from several miles away. But while their existence has been known for many years, the mechanism by which they are produced wasn't clear.
Now, though, researchers at the University of Vienna have removed the larynx from an elephant - which died of natural causes, they hasten to point out - and blown air through it to find out.
When they manually placed the vocal folds into the 'vocal' position, they found they produced periodic, low-frequency vibrations that match infrasounds in all details.
It shows that the sounds don't originate, as many scientists suspected, in the same way as a cat's purr, by tensing and relaxing the muscles of the larynx. Instead, they're produced in the same way as human speech, with the low frequency caused by the much lager size of the larynx.
The team was also able to get a very clear look at some interesting types of vibration called 'nonlinear phenomena'. When a baby cries, or a heavy metal singer screams, the vocal folds vibrate in an irregular manner, which is very grating to the ears. In the case of a baby, the reason is presumably to attract attention as quickly as possible.
Young elephants also scream and roar, says the team, and the mechanism they use is again identical to that seen in humans.