"The Jurassic Park films have got it wrong. A lot of the early reconstructions of dinosaurs have been influenced by what we associate with scary noises today from large mammalian predators like lions. In the Jurassic Park movies, they did use some crocodilian vocalisations for the large dinosaurs, but on screen, the dinosaurs have their mouths open like a lion roaring. They wouldn't have done that, especially not just before attacking or eating their prey. Predators don't do that – it would advertise to others nearby that you have got a meal, and it would warn their prey they are there," said Julia Clarke, a palaeontologist at the University of Texas at Austin.

Just imagine it. For so long, the world has believed that large dinosaurs, especially the Tyrannosaurus Rex, produced frightening roars. Every dinosaur movie features such terrifying sounds that could make your skin crawl -- combined with images of hideous creatures whose enormous, sharp teeth could rip any flesh.

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But, according to the latest findings on these giant reptiles and how they produced sounds, the world is most probably wrong in thinking that the T. rex and many other similar creatures communicated with ground-shaking rumbles. Most of the dinosaur fossils that have been dug up did not have any remains of their sound organs. And so, we've associated their sound production with the way mammalian predators make them, such as the lion roars.

However, based on the latest study of Dr. Clarke and her colleagues using advanced CT scanning techniques, they discovered that a dinosaur's sound organ could be fossilized, such as the mineralized rings of a syrinx that they found on a specimen of a Vegavis iaai -- a goose-like creature that co-existed with non-avian dinosaurs in the late Cretaceous period. However, most of the dinosaur fossils did not have any trace of voice boxes at all.

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Indeed, it's fascinating to learn that a herbivorous hadrosaur named Parasaurolophus tubicen, even without a voice box or larynx, could produce sounds through the musical crest on its head. From the nose of this creature, there were three hollow tubes that ran through its crest that could create sounds that are similar to the eerie bellows and growls of the southern cassowary, a flightless bird endemic to Australia.

"We didn't have preserved soft tissues, and we don't know, for example, if these dinosaurs had sound-producing organs such as mammals and birds do," explained Tom Williamson, one of those involved in the historic 1995 P.tubicen excavation. He is currently the curator of paleontology at the New Mexico Museum of Natural History and Science. "It became apparent that a sound-producing organ wasn't necessary to get the crest to resonate because it is such a long structure."

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On the part of Clarke and her colleagues, it was intriguing enough that the remnants of a sirinx of a Cretaceous bird could get preserved but none of the larynxes or voice boxes of many dinosaurs such as the T. rex ever were. Their only explanation for it is that the T. rex and other dinosaurs similar to it did not roar at all. Instead, they cooed like doves and ostriches.

Many modern birds are known for closed-mouthed vocalizations. This is how crocodiles also make their deep rumbles or bellows during mating season -- by inflating the throat. What's more, these closed-mouthed vocalizations are further supported by the uniqueness of the dinosaurs' ear structure.

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"Dinosaurs only had this single bone in their middle ear, the stapes – a key structure in translating vibrations in air, sound waves, to the inner ear that can then be processed by the brain," said Phil Manning, professor of natural history at the University of Manchester. "The stapes in dinosaurs were often quite large, almost the size of a matchstick in T. rex, meaning it was well tuned to lower frequencies. Small species of dinosaurs with smaller stapes would correlate with high-frequency sounds."

While dinosaurs lack the malleus (hammer) and the incus (anvil) that are characteristic in mammals as part of their hearing organ, the presence of cochleas in varying lengths within the inner ears of many dinosaur species proves that they were capable of hearing a wide range of sounds. And that this evolution of the cochlea took place near the beginning of the Archosaurs, which include all crocodiles and birds, according to Bhart-Anjan Bhullar, associate curator of vertebrate paleontology at Peabody Museum of Natural History, Yale University, in New Haven, Connecticut.

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"We considered all sorts of possible drivers of this transformation and realised that the only one that was consistent with all evidence was the advent of a high level of parental care, and more specifically the use of chirping 'location calls' by the babies," remarked Bhullar. "Given that baby birds and baby crocodiles chirp, it's reasonable to infer that baby non-bird dinosaurs did as well, and that their parents listened to them and cared for them just as crocodile and bird parents do. As far as what sensitivity to high-pitched sound means about the noises that adult non-bird dinosaurs made – it's an open question. I would be entirely unsurprised if most dinosaurs, and especially those closely related to birds, made a variety of noises."

Dr. Clarke further pointed out that there is a fundamental scaling relationship between sound frequency and body size. Higher frequency sounds are generally produced by small animals due to the length of these creatures' vocal cords. On the other hand, large animals create lower frequency sounds. Hence, in the case of dinosaurs, the sounds they produced were beyond human hearing, but they could probably be felt.

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