London: Male elephants use an ultrasound noise, too low for humans to hear, to find mates and to keep their herd together, researchers have found.
The low-pitched sound helps the animals to communicate over distances of up to 10 km, says a study published in the journal Science.
The elephant calls, occupying a frequency range below 20 Hertz, are not common with human singing, but researchers found that both are produced in exactly the same way, the Daily Mail reported.
The sounds are made by air being blown through the larynx or voice box as in the case of a human singer.
The researchers from Germany carried out laboratory tests on a larynx removed from an African elephant that had died naturally at a Berlin zoo.
Air under pressure was passed through the vocal cords to see if the elephant calls could be reproduced.
The sound, however, is different from cats’ purr, which is generated by muscular twitching movements of the vocal cords.