The fearsome roar of Tyrannosaurus Rex as portrayed in film has left many a cinema-goer quaking in their seat.

But new research suggests the king of the dinosaurs made a far more sinister sound.

For a new BBC documentary, naturalist Chris Packham visited Julia Clarke, professor of Vertebrate Palaeontology at the University of Texas , to test out a the theory that dinosaurs actually sounded more like birds and reptiles, than today’s predatory mammals.

“The most chilling noises in the natural world today come from predators, the howl of the wolf, the roar of the tiger, but experts now doubt that T-Rex sounded anything like them,” said Packham.

Dinosaurs are the ancestors of birds and are closely related to alligators and crocodiles, so Prof Clarke used the sound of the Eurasian bittern, which makes an unearthly booming call, and the vocalisations of Chinese crocodiles to estimate the noise T-Rex would have made.

Chris Packham with Tristan the Tyrannosaurus Rex in Berlin at the Naturkundemuseum in BerlinCredit: Gordon Welters More

When Professor Clarke scaled up the sound to match the size of the huge dinosaur the call became an ominous low rumble, subtle, yet scary enough to make the hairs on the back of your neck stand up.

In fact, the noise is akin to the rhythmic low thud of T-Rex footsteps in Jurassic Park or the sinister base notes which announced the arrival of the great white in Jaws.

Prof Clarke said that our aversion to such sounds today, which are often present in horror film soundtracks, may stem from an innate memory of the long-forgotten noises of dangerous predators.

“I feel like this sound just induces fear,” she said. “People think you need a roar to be really scary, but that is scariest sound you’ll have ever heard. I don’t know if we have some deep seated adaptive response to low frequency sounds but I would not be surprised.

Chris Packham and Professor Julia Clark hear the sound of T-Rex for the first time Credit: BBC More

“Across animals deeper sounds are a pretty true signal of larger body sizes so the kinds of sounds we were listening would correlate with a really big animal. Natural selection to fear these kinds of sounds seems really plausible.

“If we look at any of the classic dinosaur movies T-Rex is roaring. The reason we probably thought of this as appropriate is that large carnivores, most of them are mammals and those are sounds that they produce.

“But when we think about T-Rex, he is an animal that is most closely related to birds and alligators and crocodiles and those animals make very different kinds of sounds.”