Talk about a long silence – no one has heard their voices for 30,000 years. Now the long-extinct Neanderthals are speaking up – or at least a computer synthesiser is doing so on their behalf.

Robert McCarthy, an anthropologist at Florida Atlantic University in Boca Raton has used new reconstructions of Neanderthal vocal tracts to simulate the voice. He says the ancient human's speech lacked the "quantal vowel" sounds that underlie modern speech.

Quantal vowels provide cues that help speakers with different size vocal tracts understand one another, says McCarthy, who was talking at the annual meeting of the American Association of Physical Anthropologists in Columbus, Ohio, on April 11.

"They would have spoken a bit differently. They wouldn't have been able to produce these quantal vowels that form the basis of spoken language," he says.