What Did a T-Rex Actually Sound Like?

Tyrannosaurus rex almost certainly did not produce the thunderous, lion-like roar that Hollywood has made iconic. The best current evidence points toward something far stranger and, to modern ears, far less cinematic: deep, resonant booms and low-frequency rumbles that you might feel in your chest before you heard them clearly. Reconstructing the voice of an animal that has been dead for 66 million years is inherently speculative, but fossil anatomy, the physics of sound production, and the vocalizations of living relatives have converged on a picture that keeps getting clearer and more surprising.

Why the Movie Roar Is Almost Certainly Wrong

The roar audiences associate with T. rex in film is typically a sound-design mashup of mammalian vocalizations: big cats, elephants, sometimes dogs. The problem is that T. rex was not a mammal. It was a theropod dinosaur, and its closest living relatives are birds and crocodilians. Neither group roars in the way a lion does. Lions produce their roars using a larynx with uniquely elastic vocal folds, a feature specific to certain mammals and not found in any known reptile or bird. There is no anatomical reason to think a tyrannosaur possessed anything similar.

The vocal organ that gives birds their extraordinary range of sounds is the syrinx, a structure located deep in the chest where the trachea splits into the two bronchi. A fossil syrinx has been found in only one Mesozoic species so far, a duck-like bird called Vegavis iaai that lived near the end of the Cretaceous. The researchers who described that fossil noted that the absence of syrinx remains in any non-avian dinosaur, combined with the fact that the syrinx’s cartilaginous rings are poorly mineralized in animals that lack one, suggests the syrinx was a late innovation in bird evolution, appearing well after flight itself had already developed.¹ In other words, T. rex almost certainly did not have one. Without a syrinx and without mammalian-style vocal folds, the animal could not have produced the kinds of high-pitched, modulated screams or roars we see in the movies.

Closed-Mouth Booms and Coos

If T. rex did not roar, what did it do? One of the most compelling hypotheses comes from studying how large birds vocalize today. Many big-bodied birds, from ostriches to cassowaries to certain pigeons and doves, produce sounds with their mouths closed, inflating their throats or esophageal pouches and letting resonance do the work. These closed-mouth vocalizations tend to be deep, booming, and low in frequency. They carry well over distance but lack the sharp, high-pitched qualities humans associate with aggression.

A study mapping vocal behavior across the bird family tree found that closed-mouth vocalization has evolved independently at least 16 times in birds, and it appears predominantly in large-bodied lineages. The researchers used ancestral-state reconstruction to argue that this behavior was probably not ancestral in birds but kept emerging wherever body size increased. Given that non-avian dinosaurs included some of the largest land animals ever to live, the study suggested that the capacity for closed-mouth vocalization was present in at least some of them.² The authors even noted that an ambiguous ancestral state was recovered for vocalization behavior at the base of the archosaur tree, the group that includes both dinosaurs and crocodilians, meaning we cannot be sure whether the common ancestor vocalized with an open mouth, a closed mouth, or both.

For T. rex specifically, this would mean something more like the resonant boom of a cassowary or the low thrum of an ostrich than anything you would expect from a predator weighing around eight tonnes. Think less of a roar and more of a sound you might mistake for distant thunder or a very large drum being struck.

What Tyrannosaur Ears Reveal About Tyrannosaur Voices

One of the cleverest indirect approaches to this question is to study what tyrannosaurs were built to hear. Animals that rely on vocal communication tend to produce sounds within the range their own ears are best tuned to detect. CT scans of tyrannosaur braincases have revealed details about the inner ear, and those details are telling. The cochlea in tyrannosaurs is elongate, and the skull shows extensive tympanic pneumaticity, meaning air-filled spaces surrounding the middle ear. Both features support an emphasis on low-frequency sound perception.³

This is consistent with the closed-mouth boom hypothesis. If tyrannosaurs were tuned to pick up low-frequency sounds, it makes sense that they would have produced low-frequency sounds. Low frequencies also travel farther through dense environments like forests, which means a deep boom would have been an effective way to communicate across the large territories a top predator would have maintained. For comparison, elephants produce infrasonic calls that travel kilometers through woodland, and those calls are well below the range of human hearing. A tyrannosaur’s vocalizations could have operated in a similar acoustic niche.

The Crocodilian Connection

Birds are the only living dinosaurs, but crocodilians are the next closest living group, and their vocalizations are revealing in a different way. American alligators bellow: a deep, guttural sound produced with the mouth closed or barely open, often accompanied by visible vibrations of the water surface around the animal’s body. These bellows are used in territorial and mating displays.

Research on alligator bellows has shown that the spacing of resonant frequencies, called formants, provides reliable acoustic information about the animal’s body size. Larger alligators produce formants that are spaced farther apart, giving the bellow a deeper, more rumbling quality.⁴ This is relevant to T. rex because the same physics would apply to any large animal with a long vocal tract and resonant body cavities. A tyrannosaur’s vocal tract would have been far longer than an alligator’s, and its body far more massive, so formant spacing would have pushed the perceived sound even deeper. The resulting vocalization would not have sounded exactly like an alligator, but the underlying mechanism of closed-mouth, resonance-driven, low-frequency sound is probably the right ballpark.

Alligator bellows have an eerie quality that is hard to describe in text. They are more felt than heard at close range, a sort of pressure wave accompanied by a subsonic vibration. Scale that up by a factor appropriate to an animal ten times the mass, and you begin to get a sense of what a T. rex encounter might have sounded like: something primal and unsettling that your ribcage noticed before your ears fully processed it.

Fossil Evidence From an Ankylosaur’s Throat

Direct fossil evidence of dinosaur vocal anatomy is extraordinarily rare, because the relevant structures are made of cartilage that almost never preserves. That is why a 2023 paper describing the fossilized larynx of Pinacosaurus, an armored ankylosaur, generated so much interest. The specimen preserved a cricoid bone and arytenoid cartilages, the key structures of the larynx, in enough detail to compare them with living animals.

The researchers found that the Pinacosaurus larynx was large and kinetic, with features that resembled those of birds rather than those of lizards, snakes, or crocodilians. The firm joint between the cricoid and arytenoid, the prominent arytenoid process, and the overall size of the laryngeal apparatus all pointed toward an animal that used its larynx as a sound modifier, not as a sound source. In modern birds, the sound source is the syrinx, and the larynx fine-tunes that sound on its way out. In lizards and other non-avian reptiles, by contrast, the larynx itself generates sound through vibrating membranes.⁵

Pinacosaurus is not a tyrannosaur, and ankylosaurs are only distantly related to theropods within the dinosaur family tree. But the finding has broad implications. It demonstrates that bird-like vocal modification was already present in non-avian dinosaurs, potentially long before the evolution of the syrinx in true birds. If an armored, tank-bodied herbivore had a sophisticated sound-modifying larynx, it is reasonable to suspect that theropods, which are much more closely related to modern birds, had comparable or more advanced vocal hardware. The researchers proposed that bird-like vocalization likely appeared in non-avian dinosaurs before the origin of birds as we know them.

The Role of Air Sacs and Resonating Chambers

Theropod dinosaurs, T. rex included, had an extensive system of air sacs connected to their lungs, similar to the system that allows modern birds to breathe so efficiently. These air sacs extended into the bones of the skeleton, creating pneumatic (air-filled) spaces in the vertebrae, ribs, and even parts of the skull. This system was not primarily about vocalization; it evolved for respiratory efficiency. But as a side effect, it created a network of resonating chambers throughout the body that could have profoundly influenced the quality and carrying power of any sound the animal produced.

We see a loose parallel in living animals. Male reindeer possess an inflatable laryngeal air sac that expands dramatically during the breeding season. In adult males, this sac can reach a volume of three to four liters, and it functions as an additional acoustic filter, altering the quality of the animal’s hoarse rutting vocalizations. The neck swelling during vocalization also serves as a visual signal to rivals and potential mates.⁶ The air sac systems in theropod dinosaurs were far more extensive than a reindeer’s single laryngeal pouch, and while they were structurally different, the physics are similar: any air-filled chamber adjacent to the vocal tract can add resonance, alter timbre, and change how the sound is perceived by a listener.

For T. rex, this means the sound would not have been a simple tone produced at one point in the throat and broadcast outward. It would have been filtered and reshaped by the geometry of the skull, the length of the trachea, and the air-filled spaces in the cervical vertebrae. The result could have been a complex, textured sound with overtones and a quality that no single living animal perfectly replicates.

What About Hissing, Clicking, or Other Non-Vocal Sounds

Vocal communication is only one piece of the puzzle. Many living archosaurs make non-vocal sounds that play important roles in their behavior. Crocodilians slap the water with their jaws and clap their jaws shut with an audible crack. Various birds produce mechanical sounds using feathers, bills, or inflated throat patches. It is entirely plausible that T. rex supplemented whatever vocal sounds it could make with non-vocal sounds produced by jaw claps, foot stomps, or other physical actions. A jaw with the bite force attributed to T. rex, snapping shut in a threat display, would have produced a percussive crack audible at considerable distance.

There is also the simple act of breathing. A nine-tonne animal with a massive chest cavity and a system of air sacs would have moved an enormous volume of air with each breath. Even heavy, forceful exhalations could have been audible, producing a hissing or huffing sound. Observers of large captive crocodilians often note that the animals’ breathing is itself a sound worth noticing at close range. For T. rex, something analogous, amplified by body size and internal resonance, could have been part of the acoustic repertoire even without any active vocalization at all.

Why Movies Keep Getting It Wrong (and Probably Always Will)

The reason the cinematic T. rex roar persists is simple: a deep, subsonic rumble does not work as a movie sound effect. Sound designers need something that makes audiences flinch, something that registers as dangerous on an instinctive level. A bass-heavy, closed-mouth boom at frequencies near the lower edge of human hearing would be impressive in person but falls flat when played through standard theater speakers. A roar blended from big cats and elephants, on the other hand, triggers every predator-alarm circuit in the human brain. The movie version is effective storytelling. It just is not paleontology.

Some science documentaries have attempted more realistic sound reconstructions, using alligator bellows and cassowary booms as starting points and pitch-shifting them downward. The results tend to be eerie and unsettling, more like a natural disaster warning than an animal vocalization. Audiences who hear these reconstructions often describe them as scarier in a different way: less “monster at the gate” and more “something enormous is close and you cannot see it.” That reaction is probably closer to what a low-frequency tyrannosaur vocalization would have actually felt like to a creature within earshot during the late Cretaceous.

How Confident Can We Be

The honest answer is: moderately. We are dealing with inferences piled on inferences. No fossilized T. rex vocal organ has ever been found, and the soft tissue responsible for sound production in any animal decays long before fossilization typically begins. What researchers have to work with are the bony landmarks left behind by soft tissues, the structure of the ear and brain, the vocal anatomy of living relatives, and the physical principles that govern how sound works in bodies of different sizes and shapes.

Each line of evidence individually is suggestive, not conclusive. But when the elongate tyrannosaur cochlea points to low-frequency hearing, and the closed-mouth vocalization analysis of modern birds points to low-frequency sound production in large archosaurs, and the alligator formant research shows how body size maps onto acoustic output, and the ankylosaur larynx fossil shows bird-like sound modification in non-avian dinosaurs, the convergence is hard to dismiss. The specific pitch, volume, and quality of a T. rex vocalization remain uncertain, but the general character, deep, resonant, low-frequency, and unlike anything a mammal produces, is supported by multiple independent lines of evidence.

What researchers still disagree about is whether T. rex was particularly vocal at all. Some paleontologists have argued that certain dinosaur lineages may have been relatively quiet animals, communicating more through visual displays (crests, coloring, body posture) than through sound. The elaborate crests on hadrosaurs and lambeosaurs, which contained hollow nasal passages that could have functioned as resonating tubes, suggest that those lineages invested heavily in acoustic signaling. Whether tyrannosaurs did the same, or relied more on other senses, remains an open question. The sensory evidence from the braincase favors at least some acoustic communication, but “some” spans a wide range from occasional territorial grunts to a complex social vocabulary.

Other Dinosaurs Might Have Sounded Stranger Still

Tyrannosaurs get the most public attention, but other dinosaur groups offer even more intriguing vocal puzzles. Hadrosaurs like Parasaurolophus had elaborate hollow crests connected to the nasal passages that could have functioned as resonating chambers, essentially biological trombones. Physical and digital models of these crests have produced deep, foghorn-like tones when air is pushed through them. Unlike T. rex, Parasaurolophus left behind a bony structure that directly constrained the acoustics, so the reconstructions are on firmer ground.

Sauropods, the enormous long-necked dinosaurs, present a different puzzle. A trachea several meters long would have produced extremely low-frequency sounds simply because of the physics of tube resonance. Whether sauropods vocalized at all is unknown, but if they did, those sounds could have been in the infrasonic range, below the threshold of human hearing entirely. You would have felt a sauropod call in your bones and in your stomach, not in your ears. The Mesozoic soundscape was almost certainly far stranger than any movie soundtrack has yet attempted to capture.