Elephant Infrasound: The Seismic Rumble of Communication Scientists Are Still Mapping

In 1984, a musician named Katy Payne was standing near the elephant enclosure at Washington Park Zoo in Portland, Oregon, when she felt a throbbing in the air, not heard, felt. The sensation reminded her of sitting near a pipe organ during the lowest pedal notes. She had spent years studying whale song. She knew what infrasound felt like. When she returned with recording equipment and slowed the tapes down, she found it: elephants were talking in frequencies the human ear cannot reach.

That single observation opened a field. Payne, working later with Cornell University's Bioacoustics Research Program, established that African elephants produce calls as low as 14 Hz, well below the human hearing threshold of 20 Hz. These weren't random vibrations. They were structured, intentional, and travelling distances that seemed impossible for a land animal's voice.

Frequency is measured in hertz, cycles per second. A healthy young human ear detects sound between 20 Hz and 20,000 Hz. Elephant rumbles sit between 14 Hz and 35 Hz at their lowest registers. At those frequencies, sound waves are physically long, sometimes longer than 20 metres, and long waves lose very little energy as they move through air. A 20 Hz call from an elephant can carry clearly across 10 kilometres of open savanna. Some researchers estimate the range extends further under ideal atmospheric conditions, particularly in the early morning when temperature gradients are favourable.

Elephants generate these calls in the larynx, but the mechanism differs from human speech. A 2012 study published in Science by Christian T. Herbst and colleagues used laryngoscopy on a deceased Asian elephant to confirm that elephant vocalisation works through flow-induced vibration, the same physical principle that produces sound in human vocal folds, rather than active muscular contraction alone. The larynx of an African elephant is the largest of any land mammal, and the vocal folds are correspondingly massive, capable of vibrating at extremely slow rates that produce those sub-20 Hz fundamentals.

The air is only part of the channel. Caitlin O'Connell-Rodwell, a Stanford University researcher who has spent decades studying elephants in Etosha National Park in Namibia, demonstrated that elephant calls create seismic waves, vibrations that travel through the ground, and that elephants detect these waves through their feet and through bone conduction up their legs and into the inner ear. Her experiments showed that elephants responded to playback of seismic signals even when airborne sound was masked. They shifted weight, froze, oriented their bodies toward the signal source.

The anatomy supports this. Elephant feet contain a fatty, gel-like tissue that is highly sensitive to vibration, similar in function to the acoustic fat found in the lower jaw of dolphins, which channels underwater sound to the ear. The pacinian corpuscles in elephant foot pads are mechanoreceptors tuned to low-frequency ground vibration. In effect, an elephant standing still is also listening through the ground it stands on.

This dual-channel system, airborne infrasound and seismic detection, means elephant communication operates across two physical media simultaneously. A call sent from one herd can be received by another kilometres away through the air, and potentially through the ground as well, though the relative contribution of each channel in natural conditions is still being worked out.

The calls are not simple. Researchers have catalogued dozens of distinct infrasound call types in African elephants, each associated with different social contexts: contact calls between separated family members, musth rumbles from sexually active males that signal hormonal state to females across large distances, coalition calls that coordinate group movement, and post-copulatory calls that can involve multiple animals vocalising together in what field researchers describe as a chorus. Joyce Poole, who has studied African elephant behaviour since the 1970s and co-founded ElephantVoices, has documented that female elephants can distinguish the contact calls of over 100 other individuals, a level of vocal recognition that rivals some primate species.

Musth rumbles are particularly well-studied. Males in musth, a periodic state of elevated testosterone, produce a distinctive low-frequency call that females can detect from several kilometres. Females actively approach males in musth in response to these calls, and the calls carry information about the male's identity and likely his physical condition. The seismic component of musth rumbles has been detected by geophones placed in the ground at distances exceeding 1.5 kilometres in O'Connell-Rodwell's field experiments.

The unmapped territory is large. Researchers do not yet have a complete catalogue of infrasound call types for Asian elephants, a different species with different social structures and different habitat acoustics. Forest-dwelling elephants present a particular challenge: dense vegetation changes how both airborne and seismic signals propagate, and the call repertoire of forest elephants may differ substantially from that of savanna populations. Long-term recording projects in the Congo Basin are accumulating data, but analysis is slow.

The question of exactly how much information travels seismically versus through air in real-world conditions remains open. Lab and semi-controlled field conditions have confirmed seismic detection, but quantifying the actual contribution of ground vibration to natural herd coordination requires simultaneous measurement of both channels across multiple animals, a logistical challenge that current technology is only beginning to address. There is also the question of whether elephants produce calls specifically optimised for seismic transmission, or whether the seismic signal is simply a byproduct of powerful airborne calls. The two hypotheses have different implications for how the communication system evolved.

The picture is also complicated by the discovery that elephant infrasound interacts with environmental noise in ways researchers did not initially anticipate. Road traffic, industrial activity, and seismic noise from human sources all fall in the frequency range elephants use. Studies in fragmented habitats in India, including work in and around protected areas in Karnataka and Assam, have raised questions about whether anthropogenic low-frequency noise is degrading the effective range of elephant communication in landscapes where human activity is intensifying.

What Payne felt as a throbbing in the air in 1984 has turned out to be one layer of a communication system that uses the physical world more completely than almost any other land animal's. The seismic channel, the infrasound channel, and the social memory required to interpret both, these aren't separate facts about elephants. They are the same fact, seen from three angles: that an animal large enough to shake the ground found a way to make that shaking carry meaning.