We’re more than 66 million years too late to know what tyrannosaurs or triceratops sounded like. The fossil record just doesn’t preserve dinosaurs in enough detail to know what all of their organs looked like or how they functioned. The roars and bellows of the movies are, more often than not, mashups of living-animal sounds.
But that’s not to say the Mesozoic has to be a silent movie in our imaginations. Dinosaurs probably made sounds by clapping their jaws, rubbing their scales together, and swooshing their tails, just like some modern reptiles do. And when it comes to vocalizations, some dinosaurs left us with some sound bites.
Hadrosaurs like Parasaurolophus and Corythosaurus had large, hollow crests with extended nasal passages. By blowing air through these passages, we can get an idea of some of the sounds they made — low, booming calls not unlike a foghorn. The inner ear anatomy of these dinosaurs matches up with the sounds we expect from their ornate headgear. Around 75 million years ago, it would’ve been possible to hear the cacophony of a Cretaceous traffic jam.