The terrifying roar of a Tyrannosaurus rex sent shivers down the spines of audiences who went to see Jurassic Park at the cinema.

But new research suggests dinosaurs may have produced a feeble sounding cooing noise rather than the Earth-shaking roar depicted on the big screen.

The study examined how birds, the modern ancestors of the dinosaurs, produce calls with their mouths closed using a specialised vocal organ in their neck.

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The roaring dinosaurs depicted in the Hollywood film Jurassic Park (pictured) may have been more like the cooing of a dove, according to new research by scientists. Researchers looked at the evolution of closed mouth vocalisation in birds and reptiles and found it has evolved several times though out history

By looking at how this ability evolved in birds sheds light on how dinosaurs may have also produced sound, according to the researchers.

DID T-REX HAVE A POUT? The fearsome undisputed king of dinosaurs may need to undergo an image makeover if new research by palaeontologists turns out to be correct. In the past researchers have claimed Tyrannosaurus rex likely had an exceptional sense of smell, may have been covered in feathers, may have scavenged rather hunted. But now, according to one scientist in Canada, the giant carnivore also had a set of lips covering its sharp, sizeable gnashers. According to palaeontologists in Toronto, a closer look at the fearsome jaws of toothy reptiles alive today revealed tell-tale traces on the animals' teeth, which indicate the presence of lips. Teeth have a low water content and need a moist environment to help prevent decay and the erosion of the protective enamel. While crocodiles lack lips, their teeth are kept moist by their aquatic environment. Whereas monitor lizards – many of which live in desert environments – have lips to cover and protect their teeth. Analysis of recovered dinosaur teeth shows they had well preserved enamel – a sign they were protected by a covering of soft tissue. Advertisement

These closed-beak vocalisations are created by the bird pushing air into a pouch in their neck. This creates a muffled sound that is generally much deeper than other calls made by birds.

Doves use this to produce their distinctive cooing noise while ostriches also use it for their strange booming mating call.

'Looking at the distribution of closed-mouth vocalization in birds that are alive today could tell us how dinosaurs vocalized,' said Chad Eliason, a postdoctoral researcher at the University of Texas and the study's co-author.

'Our results show that closed-mouth vocalization has evolved at least 16 times in archosaurs, a group that includes birds, dinosaurs and crocodiles.

'Interestingly, only animals with a relatively large body size - about the size of a dove or larger - use closed-mouth vocalisation behavior.'

To conduct their study, which is published in the journal Evolution, the scientists used a statistical approach to analyse the distribution of this vocal ability among birds and other reptilian groups.

In total, the researchers identified 52 out of 208 investigated bird species used closed-mouth vocalisation.

Professor Tobias Riede, a physiologist at Midwestern University and the study's first author, said the association with large bodies is a matter of physics.

'The inflation of an elastic cavity could present a size-dependent challenge,' said Professor Riede said.

'The lung pressure required to inflate a cavity depends on the tension in the wall of the cavity, and this tension increases for smaller body sizes.'

The researchers analysed 208 species of bird and reptiles and found that 52 produced closed mouth vocalisations including doves, ostriches and crocodiles (illustrated)

Despite the depictions in Hollywood films, scientists still have little idea about the noises produced by dinosaurs and their extinct relatives.

Fossil evidence is unable to provide information about the soft tissue needed to produce and control vocalisations.

However, both birds and crocodiles – the two surviving groups of archosaurs – produce closed mouth vocalisations and can give clues about how dinosaurs may have communicated.

Doves (pictured) are one of the 52 species identified by the scientists that use closed mouth vocalisations

The noise produced by air being pushed into the oesophageal pouch transmits sound through the skin and muscle.

In crocodiles, these closed mouth vocalisations create a deep rumbling territorial call that can often make the water dance due to the vibrations.

In large dinosaurs it is likely such vocalisations would be very deep indeed and may even have been beyond human hearing.

It raises the tantalising prospect that the animals could have used low frequency communication like infrasound – something that large mammals like elephants are known to do today.

Professor Riede said the occurance of closed-mouth vocalisation in crocodiles and birds makes it likely that at least some dinosaurs may also have evolved this method of communication.

Birds produce these closed mouth vocalisations by forcing air into a pouch in their neck, which causes the skin and muscle in their neck to vibrate (X-ray a ring dove producing cooing sounds with a closed mouth)

He said: 'A cool thing about this work is the demonstration that closed-mouth behavior evolved many times.

'That suggests it can emerge fairly easily and be incorporated into mating displays.'

Professor Julia Clarke, a palaeontologist at the Jackson School of Geosciences who was also involved in the study, said genetic studies and modelling could help to reveal more about the noises produced by dinosaurs.

She added: 'To make any kind of sense of what nonavian dinosaurs sounded like, we need to understand how living birds vocalize.

'This makes for a very different Jurassic world. Not only were dinosaurs feathered, but they may have had bulging necks and made booming, closed-mouth sounds.'