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A Tyrannosaurus rex skeleton standing in a natural history museum atrium.
Did this T-rex roar, or honk?
Mark Wilson/Newsmakers/Getty Images

What did dinosaurs actually sound like? Take a listen.

Two tubas, a chicken, and a low-pitched alligator: The weird ways scientists imagine dinosaur voices.

No one on Earth has ever heard a dinosaur roar. But that hasn’t stopped scientists and filmmakers from wondering: What did dinosaurs sound like?

The most famous answer might be from the movie Jurassic Park, which featured dinosaur roars that sounded something like this:

This is a scary noise, but it’s likely not realistic. Dinosaurs were reptiles, but when the Jurassic Park sound designers created their roars, they mainly constructed them from mammal sounds — from recordings of tigers, lions, koalas(!), donkeys, dolphins, and elephants.

There’s no scientific basis for a T. rex sounding like a donkey. Instead, the filmmakers were trying to evoke the feeling of being in the presence of a dinosaur. (Jurassic Park sound designer Gary Rydstrom once responded to a scientist’s critical question of the film by laughing, saying, “It’s a movie.”)

Figuring out what dinosaurs actually sounded like is an almost impossible task, because scientists can’t exactly dig up a fossilized roar. “Most of the sound-producing structures are soft tissues or less resilient hard tissues,” paleontologist Michael Habib says on Unexplainable, Vox’s science podcast about unanswered questions. “It’s muscle and cartilage, and those tend not to fossilize.”

Still, scientists think it’s an important question. Figuring out what dinosaurs sounded like means understanding the world they lived in a bit better, and is a key to understanding how they behaved.

To start, the shapes of dinosaur skeletons do provide some hints. One dinosaur, called parasaurolophus (a.k.a. Ducky from The Land Before Time), had a long chamber in its skull, which allowed scientists to estimate the general frequencies that could have resonated within its head. But this chamber doesn’t tell us about the actual dinosaur voice that fed into it.

Still, all hope is not lost. In order to figure out what an actual dinosaur voice may have sounded like, scientists can look to dinosaur relatives that are still alive.

“We have to do the best we can,” Habib says, with the clues scientists have. These are the most promising leads.

Crocodilians make low-pitched rumbles. Maybe a T. rex did, too.

Scientists can look to living relatives of dinosaurs to reconstruct their sounds. If they share a common ancestor, they may have similar attributes as well, like how they make sound.

One such related group is crocodilians (crocodiles, alligators, caimans), who share a common ancestor with dinosaurs that lived around 250 million years ago.

If you watch Jurassic Park, you’ll see a T. rex opening its mouth to roar, but if T. rexes are more like crocodilians, they probably would have made more of a low-pitched, closed-mouth rumble.

“They’ll rumble so powerfully that you see ripples all around them on the water,” says Habib of crocodilians. “They’re shaking the pond, basically.”

Bigger animals tend to make lower-pitched sounds than smaller animals do. So imagine a huge dinosaur, many times bigger than a common crocodile; it’s possible that this dinosaur made a very low-pitched, closed-mouth crocodilian rumble.

Paleontologist Julia Clarke actually made a demonstration of this with the BBC, pitching an alligator sound down extremely far in order to simulate what a T. rex may have sounded like:

As the pitch drops further, it approaches the range known as infrasound. Just as infrared light is too long of a wavelength for a human to usually see, infrasound waves vibrate so slowly that it can be hard for a human to hear. So if dinosaurs did sound like an ultra-low-pitched crocodilian, a lot of their sounds could have been hard to hear. Ear hairs are too small to vibrate as a result of this sound, but bigger parts of the body could have vibrated.

If a human were sent back in time, they might have actually felt the sound in their legs or chest. Terrifying!

Birds are even closer relatives to dinosaurs, so could dinosaurs have sung?

Crocodiles are a good starting point for imagining what dinosaurs might have sounded like, but they’re not dinosaurs’ closest relatives.

That honor goes to birds, the direct descendants of dinosaurs. “I used to put a roast chicken on the docu-viewer in the classroom,” says Clarke. “You can see the assembly of those structures that are in your roast chicken in the fossil record.”

So how can birds potentially teach us about what dinos sounded like? A clue: Birds have a unique vocal organ. Most vertebrates make sounds using their larynx, a vocal organ located in the throat, but birds use a syrinx, a vocal organ located deep in the chest, next to the heart. Clarke likes to joke, “Birds sing from the heart.”

Because a syrinx is located deep in the chest, it produces sound more efficiently, which is why small birds can make such loud noises. Also, unlike a larynx, a syrinx actually has two openings, so birds can produce multiple pitches at once. “They can sing a duet with themselves,” says Habib. The wood thrush, for example, does this, singing two notes at the same time.

But if birds are actually tiny dinosaurs, why consider crocodilian sounds at all? The issue is that scientists aren’t sure when syrinxes first appeared. Clarke has found a syrinx from 67 million years ago (about a million years before large dinosaurs went extinct), but this syrinx was from an ancient duck relative, not a huge dinosaur. She hasn’t yet found concrete evidence of a huge dinosaur with a syrinx.

But because syrinxes are soft structures, finding evidence of them is difficult. (Clarke’s syrinx was an extremely rare discovery.) So it’s possible there are other even more ancient syrinxes out there, waiting to be unearthed.

Dinosaurs singing a duet with themselves?

If scientists were to confirm dinosaurs had syrinxes, it would open up a world of sonic possibilities. Dinos might have sounded similar to large, flightless birds like ostriches or emus, which can produce all sorts of whistles, guttural bellows, and throaty clicks.

But the bigger a dinosaur, the weirder it would have sounded. Habib describes a potential huge dinosaur syrinx sound as a “tuba honk.” “It’s like a pulse,” he says. “A very low sound. Bruhhhhhm, bruhhhhhm, bruhhhhhm.” Habib actually made this noise to me over the phone:

But wait. It can get way weirder. A syrinx would have allowed a dinosaur to make two sounds at once, so Habib can really let his imagination run wild: “Get two tubas. And have them play to different notes over top of each other as loud as they can. It’s just this kind of war rumble.”

It’s also possible that dinosaurs sounded like a mash-up between birds and crocodilians. Habib says they might have been able to make open-mouth sounds like birds and closed-mouth crocodilian sounds together.

Here’s what he imagines:

They might be doing open-mouth sounds with two different tones and then could also do closed-mouth sounds that would be a rumble. And they could switch between the two, which means that they could rumble, and while your body is still shaking from the rumble, they can open their mouth and blast you with two non-infrasound but still very low notes, while things are still kind of shaking from the rumble. It could get real interesting.

Habib is quick to caution that because we don’t know whether huge dinosaurs had syrinxes, this is all speculative. “The more conservative estimate would be to use crocodilian-based sounds” to imagine dinosaurs, he says. “But the best is probably some careful combination of all the above.”

On this week’s episode of Unexplainable, Vox sound designer Cristian Ayala tried his hand at creating some scientifically plausible dinosaur sounds based on these conversations. Here was his process in assembling a new T. rex sound, based on what we learned from paleontologists.

He started with a chicken’s “b’caw,” pitched it down, and added the noise of a sandpiper (and Unexplainable producer Mandy Nguyen’s pigeon, Sunny), layering the noises at different frequencies on top of each other. There’s a little tuba influence and some ostrich, emu, and alligator sounds as well.

Is this what a T. rex actually sounded like? No one knows!

But it’s likely to be a more accurate representation than what you’ll hear in Jurassic Park. The scientists I spoke to emphasized that this exercise is more than just trivia. Sound is important because it shows how ancient animals communicated, how they moved, how they lived. Scientists may never know exactly what this world sounded like, but in attempting to recreate dinosaur sounds, they can imagine, if only slightly better, the world these creatures lived in.

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