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Elephants Speak in Voices Too Deep to Hear

Most elephant calls are low-pitched rumbles below the range of human hearing.

Key points

  • Most elephant calls are below the frequency of 20 Hz, which puts them outside the range of human hearing.
  • Elephant calls may be inaudible to us, but they're not quiet. An elephant's infrasonic rumble can be as loud as a chainsaw or an ambulance siren.
  • Elephants use their rumbles to say hello, give directions, and warn each other of danger.
Source: Nilina/Pexels
Two elephants playfully interact with one another.
Source: Nilina/Pexels

Imagine yourself standing on the savanna. You can't see any animals nearby, but suddenly you feel a thrumming in the air around you. You may be sensing elephants speaking to each other.

Elephants are capable of a huge range of vocalizations, from roars to squeaks. However, most of the sounds they make can’t be heard by the human ear.

These low-pitched noises are known as infrasound, meaning “below sound,” because they’re too deep for humans to hear. A human child with perfect hearing can pick up sounds from frequencies of about 20 to 20,000 Hz. The range of sounds we can actually voice is even narrower, from around 65 Hz for a bass singer’s low C to around 1,550 Hz for a soprano’s ear-splitting G6, a note almost three octaves above middle C.

Elephants’ infrasonic calls, often referred to as “rumbles,” have been recorded at frequencies as deep as 5 Hz, well below the lower limits of our hearing. Just because we can’t hear these sounds, though, doesn’t mean they’re not loud. An elephant’s booming rumble can reach volumes of up to 117 dB, as loud as a chainsaw or an ambulance siren.

Discovering Elephant Infrasound

Biologist Katy Payne discovered that elephants were capable of making infrasounds in 1984 when she felt a kind of throbbing in the air while visiting the elephant enclosure at a zoo.

"I realized that was the same feeling I got when I used to sing at Cornell in the Sage Chapel," Payne recalled in an interview with NPR.

It would go low, low, low. When the pipes go down, you begin to lose pitch – and pitch is replaced by feeling. I thought, Maybe the elephants are making sounds too low for me to hear, but powerful enough to feel.

A specialist in bioacoustics, Payne was the same researcher who had recognized twenty years earlier that humpback whale sounds were actually structured songs. After her experience at the zoo, Payne founded the Elephant Listening Project, which monitors the sounds made by forest elephants in Central Africa.

What are elephants saying to each other?

Elephants make their low-pitched rumbles by allowing their vocal cords to vibrate while they exhale, the same way humans do when we speak. By manipulating their vocal cords, mouth, tongue, larynx, and trunk, elephants can change the sounds they produce to communicate different messages to other members of their herd.

Elephants use rumbles to greet each other and to give directions. A mating male can rumble “Back off!” to his competition, and a calf can rumble a call for its mother when it’s lost. Elephants can even rumble specific warnings to each other. In one study, researchers found that the rumble meaning “Look out! Humans!” is different from the one meaning “Look out! Bees!”

A family of elephants takes flight after hearing a bee alarm call:

Low-Frequency Sounds Travel Further

Infrasounds have a distinct advantage over higher-pitched vocalizations: they carry over long distances. On the open grasslands of the savannah, elephants can hear each other’s rumbles from distances of up to four km (2.5 miles) away.

Low-pitched calls are even more useful in the forest, where dense trees act as a filter. The short wavelengths of high-frequency sounds bounce off the trees and their leaves, but the long wavelengths of low-frequency sounds are so large they don’t get blocked by tree trunks and other obstacles.

When the forest is quiet, elephants can hear each others’ rumbles at distances of more than three km (1.9 miles) away.

This video from the Elephant Listening Project illustrates why low-pitched sounds travel further in a forest than high-pitched ones:

How can you tell when an elephant is rumbling?

If you can’t hear it, how can you know whether or not an elephant is rumbling? The elephant’s body language can give you a clue.

Source: redcharlie/Unsplash

The Elephant Listening Project and other research teams use specialized recording equipment to detect elephant rumbles in the wild. At the same time, researchers watch the elephants to see how they behave. This is how biologists have been able to match particular rumbles to particular meanings.

It has also allowed some general observations about how elephants act when they rumble. When elephants are listening for rumbles, they open their ears wide to either side of their head and hold them still. When they’re making rumbles, they often flap their ears.

So, if you ever see an elephant, keep an eye on its body language. You might just feel a little rumble in the air.

More from Ainsley Hawthorn Ph.D.
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