There are some very strong clues that some plant-eating dinosaurs could produce a lot of noise, although we cannot be sure about this. Many duck-billed dinosaurs had a large bony structure on their head, which was probably used to amplify sound, like the body of a guitar, Hollow air passages in the bony structure allowed the dinosaur to produce low, booming cries. In some species, the shape of the crest and the sounds produced varied between individual animals, helping herd members to locate each other. Males might have used their individual sounds in mating displays. A duck-billed dinosaur called Parasaurolophus had a crest that swept back in a long curve, while others had a crest that bulged forwards.
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