Researchers have observed that elephants seem to know where other elephants are and where they are going, even when they are separated by miles of dense forest. Elephant families will suddenly stop grazing, turn their heads in the same direction, and walk into the forest. The elephants act as if they are communicating with each other.
It is believed that these elephants are responding to low frequency sounds, called infrasound. Human ears cannot hear most elephant rumbles, but sometimes humans can feel the vibrations. Infrasound vibrations are below 20 cycles per second. The frequencies of sounds normally heard by elephants and humans are shown in the table below.
RANGE OF NORMAL HEARING
| Animal | Hearing Range | |
| Minimum Frequency (cycles per second) |
Maximum Frequency (cycles per second) |
|
| Elephant | 14 | 16,000 |
| Human | 20 | 20,000 |
Katherine Payne, a researcher from Cornell University, felt vibrations in the air while she was watching the elephants at the Metro Washington Park Zoo in Portland, Oregon. She believed the elephants might be communicating using infrasound.
Payne and other researchers conducted a study on wild elephants living in southwest Africa. The researchers placed microphones and speakers in areas where elephants live. They recorded the elephants' rumbles and observed their behavior. They found that elephants “talk” to each other in frequencies ranging from 14 cycles per second to 16,000 cycles per second.
To learn how far the rumbles could be heard, they played recordings of low frequency elephant rumbles and watched the reactions of distant elephants. The researchers found that elephants hear low frequency sounds that are produced as far as two and one half miles away. The researchers did not test beyond two and one half miles. The sounds that elephants produce and hear may travel even farther.