When you picture a dinosaur — one youve seen in movies like "Jurassic World" or in a book illustration — you probably imagine a giant creature covered in scales. And when you imagine what a dinosaur sounded like, you probably think of a terrifying roar,

But the truth is, popular Hollywood depictions of dinosaurs as leathery-skinned creatures with a growl that can rattle a room are likely all wrong, experts say. For starters, paleontologists now know most dinosaurs had feathers, not scales, according to the Cornell Lab of Ornithology — and theyve known this for more than three decades. But for some reason, that knowledge hasnt yet changed how dinos appear in our imaginations — or in the media.

"Science illustrators are already embracing the new ideas, drawing and discussing cutting-edge paleontological ideas daily on their blogs. The time of the dinosaur’s dominance, from the end of the Triassic to the final catastrophic meteor strike, was not the Age of Reptiles. It was the Age of Big Weird Feathered Things. It’s just the mainstream world that is lagging behind," Stephen J. Bodio writes for the Cornell Lab of Ornithology.

Finding their voice

Hundreds of fossils, most found in China and Mongolia, prove dinosaurs had feathers and show where they attached to their bones. But when it comes to figuring out what dinosaurs sounded like, there is no fossilized evidence. To roar, animals need a voice box, but voice boxes are made of flesh, which decomposes.

To solve the puzzle, scientists look at other preserved evidence, such as the size of the rib cage, which indicates how big its lungs were, paleontologist "Dinosaur George" Blasing tells The History Channel. They compare the size of a dinosaurs chest with the size of its throat and mouth and make an educated guess that their volume would have matched their size, he says.

The shape of dinosaurs skulls also provide clues. Many of these prehistoric beasts had nasal cavities, mouths and connected noses, which created resonance chambers in their skulls, according to a study published in The Anatomical Record. Some dinosaurs, like the lambeosaurus, had massive resonating crests connected to their breathing tracks, which may have amplified noises even further.

As LiveScience reported in 2008:

When a lambeosaur made calls, air would travel through the nasal passages enclosed by the head crest. Since the sizes and shapes of head crests (and nasal passasges) differed among lambeosaurs, each one had its own voice — their calls also would have sounded distinctive individual by individual, the researchers found.

Looking to modern ancestors for clues

Birds and crocodiles are the two closest living relatives to dinosaurs. Crocs use a larynx to make sounds, and birds use a syrinx. Interestingly, both of these evolved after dinosaurs were extinct, according to Discovery News, so we know dinosaurs did not have either.

A 2009 paper published in Historical Biology says some dinosaurs may have hissed, noting that "hissing as a threat device, often directed at potential predators, is widespread among ... lizards, snakes, turtles, crocodilians, basal birds and basal mammals."