Dozens of animal species produce or detect sounds below roughly 20 hertz, the conventional floor of human hearing, and they rely on these infrasonic signals for purposes ranging from long-distance conversation to storm tracking to finding mates in dense forest. Elephants are the most thoroughly studied infrasound users on land, but the roster extends to whales, hippos, cassowaries, albatrosses, and likely big cats. The reasons different species have evolved infrasonic abilities are just as varied as the animals themselves, and recent research keeps adding new names to the list.
Elephants and the Ground Beneath Their Feet
African and Asian elephants are the textbook example of infrasound in the animal kingdom. Their deep rumbles can drop below 20 hertz, well into the infrasonic range, and because low frequencies resist being absorbed by vegetation and terrain, these calls can carry across remarkable distances.1Animal Behaviour. Long-distance communication of acoustic cues to social identity in African elephants Researchers confirmed the mechanism behind these sounds by studying an excised elephant larynx with high-speed video and showing that the vocal folds vibrate on their own when air flows through them, the same basic physics that powers a human voice, just scaled up dramatically.2PubMed. How low can you go? Physical production mechanism of elephant infrasonic vocalizations There is no special “purring” mechanism at work. The elephant simply has enormous vocal folds, and their size naturally produces frequencies that fall below what our ears can pick up.
What makes elephants truly unusual is that they seem to listen with their feet, not just their ears. Their low-frequency rumbles travel not only through the air but also through the ground as seismic waves. Field researchers noticed that elephants sometimes adopt distinct postures, leaning forward with their weight shifted onto their front feet, as though concentrating on something underfoot. Anatomical studies of Asian elephant feet found high densities of Pacinian corpuscles, vibration-sensitive nerve endings, distributed in a way that could plausibly allow the animals to pick up ground-borne signals.3PubMed Central. The distribution, density and three-dimensional histomorphology of Pacinian corpuscles in the foot of the Asian elephant (Elephas maximus) and their potential role in seismic communication This dual-channel system, airborne and seismic, could explain how separated elephant groups coordinate their movements across savannas where line-of-sight communication is impossible.
Whales and the Ocean’s Long-Range Channel
If elephants are the flagship infrasound users on land, baleen whales hold that title in the ocean. Blue whales and fin whales produce calls that can dip below 20 hertz, and in the deep ocean these sounds propagate with extraordinary efficiency. Water is far denser than air, and a channel of cold water sandwiched between warmer layers, sometimes called the deep sound channel, can act as a waveguide that carries low-frequency calls across hundreds or even thousands of kilometers.
Baleen whales, known collectively as mysticetes, are thought to use infrasound for several overlapping purposes. Males of some species produce repetitive, patterned calls during breeding season that are likely advertisements to females or warnings to rival males. But long-range contact calls also appear outside of mating contexts, which suggests that whales use infrasound simply to keep track of one another across the vast, featureless ocean. Some researchers have proposed that whales may also use infrasound for a kind of acoustic mapping, listening to how their calls reflect off the seafloor and coastlines to orient themselves during migration, though direct proof of that idea is still thin.4Environmental Science and Pollution Research. Infrasonic acoustic energy produced by offshore wind turbine energy generation may interfere with bird and cetacean navigation cues
Hippos and Their Dual-Medium Broadcasts
Hippos spend their days half-submerged in rivers and lakes, a lifestyle that creates a peculiar acoustic challenge: how do you call to a hippo that might be on land or underwater? The answer turns out to be both at once. When a hippo vocalizes in its characteristic amphibious posture, with its eyes and nostrils above the surface but its mouth and throat submerged, the sound radiates into the air and into the water simultaneously.5Animal Behaviour. Amphibious communication with sound in hippos, Hippopotamus amphibius This is unusual in the animal world. Most species communicate in one medium or the other, not both at the same time.
Hippo vocalizations include very low-frequency components, and the underwater portion of their calls can travel well through the murky water of the rivers they inhabit, where visibility is often near zero. For an animal that defends territory aggressively, being able to broadcast your identity to neighbors both above and below the waterline is a clear advantage. Other hippos can assess the caller’s size and proximity before a confrontation escalates.
Giraffes, Rhinos, and Tigers
Giraffes were long thought to be essentially silent. That reputation has eroded as researchers documented hisses, low hums, and infrasonic vocalizations from captive and wild giraffes.6Journal of Zoology. How do giraffes locate one another? A review of visual, auditory, and olfactory communication among giraffes The function of these sounds is still debated. Giraffes live in loose, fission-fusion social groups where individuals may be spread over a wide area, so low-frequency contact calls would make ecological sense, but confirming that the animals actually respond to these sounds in the wild has proven difficult. Giraffes are simply hard to record in their natural habitat without disturbing them.
White rhinoceroses produce repetitive, low-frequency “pant” calls that carry enough acoustic detail to identify individual animals and even distinguish between the northern and southern subspecies. Researchers found that these calls encode enough information to discriminate among at least nine individuals within each subspecies.7PubMed Central. Contact calls of the northern and southern white rhinoceros allow for individual and species identification For animals that are often solitary and navigate thick bush where visual contact is limited, a reliable vocal ID system is valuable.
Tigers round out this group. Their roars contain energy that extends below 20 hertz, and there is evidence that these infrasonic components can produce a visceral, paralyzing effect on prey and even on other predators. Researchers have been working to characterize the vocal properties and hearing capabilities of several surviving tiger subspecies, including Siberian, Bengal, Sumatran, and Indochinese tigers.8DigitalCommons@University of Nebraska – Lincoln. Acoustic Communication in Panthera tigris: A Study of Tiger Vocalization and Auditory Receptivity The infrasonic component of a tiger’s roar is thought to be one reason the sound feels so physically overwhelming at close range, you are not just hearing it, you are feeling it in your chest. Whether tigers deliberately exploit this effect or it is simply a byproduct of their large larynx is still an open question.
Cassowaries and the Deepest Bird Calls
Among birds, cassowaries hold the record for the lowest-pitched vocalizations. Southern cassowaries produce pulsed booming calls with energy reaching down to about 32 hertz, while the smaller dwarf cassowary pushes even lower, with fundamental frequencies around 23 to 25 hertz.9The Auk. Low-Frequency Vocalizations by Cassowaries (Casuarius Spp.) These booms are accompanied by harmonics at roughly 50, 75, and 100 hertz, giving the call a layered, resonant quality that carries through dense tropical rainforest. Cassowaries are largely solitary and live in thick undergrowth where visibility can be measured in meters, so a low-frequency call that slips around tree trunks is a practical solution to finding mates or warning rivals.
The anatomy behind these deep calls involves the cassowary’s large body size, long trachea, and possibly the bony casque on top of its head, though the casque’s exact acoustic role is still debated. What is clear is that cassowaries have converged on the same acoustic strategy as elephants: use low frequencies to punch through environments that would swallow higher-pitched sounds.
Albatrosses, Pigeons, and Infrasound as a Navigation Tool
Not every animal that uses infrasound produces it. Some are pure listeners, exploiting natural infrasonic signals in the environment for navigation. Albatrosses are a striking example. A study tracking 89 free-ranging albatrosses with GPS found that the birds did not simply follow wind patterns during their foraging trips. They also oriented toward ocean regions producing loud microbarom infrasound, the low-frequency rumble generated by colliding ocean waves and storm systems.10Proceedings of the National Academy of Sciences. Albatross movement suggests sensitivity to infrasound cues at sea Because microbarom signals propagate for thousands of kilometers through the atmosphere, an albatross that can detect them would have advance notice of distant storm fronts and the productive foraging patches that storms tend to create.
Pigeons have been suspected of infrasonic sensitivity for decades. Homing pigeons in particular seem to use very low-frequency atmospheric sounds as part of their remarkably accurate navigation. The hypothesis is that natural infrasound sources, including mountain ranges, ocean surf, and atmospheric turbulence, create a consistent acoustic landscape that a pigeon can read like a map. Laboratory studies have shown that pigeons can detect sounds down to a few hertz, far below what any human could perceive. The idea that birds in general are sensitive to infrasound is supported by anatomical evidence: low-stiffness structures in the middle and inner ear of birds, including large air cavities in the skull connected to the middle ear, appear to be adapted for transmitting very low frequencies.11PubMed. Infrasonic hearing in birds: a review of audiometry and hypothesized structure-function relationships
Sensing Earthquakes and Severe Weather
Reports of animals behaving strangely before earthquakes go back centuries, and while many of these stories are anecdotal, the underlying physics is not unreasonable. Earthquakes are preceded by foreshocks and by changes in ground vibration, electric fields, and acoustic emissions, some of which fall squarely in the infrasonic range. A review of possible sensory mechanisms concluded that some animals are far more capable than humans of perceiving geophysical stimuli below 50 hertz, and that the levels of acoustic and electrical precursors reported before earthquakes fall within the detectable range for those animals.12Reviews of Geophysics. Unusual animal behavior before earthquakes: A review of possible sensory mechanisms
The practical difficulty is turning this into anything reliable. Animals behave strangely for all sorts of reasons, and confirmation bias is enormous: nobody remembers the time the dogs were restless and no earthquake followed. Still, there are documented cases where elephants, flamingos, and other infrasound-sensitive animals fled inland or to higher ground before tsunamis struck, which is consistent with the idea that they detected the infrasonic component of the approaching wave long before humans noticed anything.
Severe weather is a more straightforward case. Thunderstorms, tornadoes, and large-scale weather fronts all generate infrasound. Birds that can detect these signals have an obvious survival advantage: they can reroute a migration or hunker down before dangerous conditions arrive. Some researchers have proposed that the sudden, seemingly coordinated departure of songbirds from a region ahead of major storms is driven by infrasonic detection rather than barometric pressure changes alone, though separating the two is experimentally tricky since storms produce both.
Insects and Vibration
Insects complicate the infrasound picture because many of them detect very low-frequency vibrations through the substrate they are standing on rather than through airborne sound. A cricket or planthopper feels the vibration of a potential mate’s call through a leaf or stem, and some of these substrate-borne signals have frequencies well below 20 hertz. Detection of these low-frequency vibrations serves multiple purposes in the insect world: species recognition and mate selection, predator avoidance, territorial defense, and even host location by parasitoid flies searching for a prey insect by eavesdropping on its calls.13Springer. Insect Bioacoustics and Biotremology
Whether this should count as “infrasound” in the same sense as an elephant rumble is partly a matter of definition. Bioacousticians increasingly distinguish between airborne infrasound and substrate-borne vibration, grouping the latter under the term biotremology. The physics differ: a vibration traveling through a plant stem behaves differently from a pressure wave in air. But from the animal’s perspective, both involve detecting mechanical energy at very low frequencies, and the evolutionary pressures that favor low-frequency sensitivity overlap considerably. Dense vegetation, noisy environments, and long distances all reward animals that can shift their communication below the frequencies where interference is worst.
When Human Noise Becomes a Problem
The growing catalog of infrasound-sensitive animals has raised concerns about anthropogenic sources of low-frequency noise. Offshore wind turbines, for instance, generate infrasonic energy both through the air and into the water via their foundations. Because birds and whales appear to use infrasonic signals for navigation and communication, the installation of thousands of turbines along coastal migratory routes could impose real costs on these animals by masking the natural infrasonic cues they rely on.4Environmental Science and Pollution Research. Infrasonic acoustic energy produced by offshore wind turbine energy generation may interfere with bird and cetacean navigation cues Shipping noise is another major contributor. Large vessels produce continuous low-frequency sound that overlaps with the communication frequencies of baleen whales, effectively shrinking the distance over which whales can hear one another.
The challenge for conservation policy is that infrasound is invisible and, by definition, inaudible to humans. Environmental impact assessments for industrial projects rarely measure noise below 20 hertz, because regulatory frameworks were built around human hearing thresholds. That gap means infrasonic pollution can accumulate without anyone noticing until an affected population starts declining. Researchers have argued that acoustic monitoring programs need to extend their frequency range downward if they are to protect species that depend on the low-frequency world.
Why Low Frequencies Keep Showing Up Across the Tree of Life
The sheer diversity of infrasound users, from insects to elephants, from cassowaries to whales, suggests that low-frequency communication and sensing have been independently reinvented many times. The physics behind it are straightforward. Low-frequency sound waves are long, which means they bend around obstacles and resist being scattered by small objects like branches, leaves, or waves. They also lose energy more slowly as they travel, giving them range that higher frequencies cannot match. Any animal that needs to communicate across a long distance, through dense cover, or in a noisy environment faces evolutionary pressure to push its signals lower.
Body size plays a role as well. Producing very low frequencies generally requires large vibrating structures, which is why the most prolific infrasound producers tend to be big animals: elephants, whales, cassowaries. But detection does not require large body size, which is why small birds and even insects can be infrasound listeners without being infrasound producers. The asymmetry between production and detection explains why the list of animals that hear infrasound is almost certainly longer than the list of animals that make it. We just have a much harder time proving that an animal is listening to something we cannot hear than proving it is producing something we can measure with a microphone.