Bad news, ladies... after listening to more than 2,200 encounters, scientists have finally worked out how to tell you're faking it

It is one of the most memorable scenes of any Hollywood romcom.

But when Meg Ryan faked an orgasm in a packed restaurant in When Harry Met Sally, it was far too noisy to be mistaken as the real thing, say scientists.

Swedish researchers claim to have discovered the sure sign of when a woman is faking it, and say ecstatic loud moans and screams – as Ms Ryan acted out in front of fellow diners – are a rarity.

The scientists listened to a staggering 34 hours of audio recordings of bedroom activity to reach their conclusions.

They said that overdoing it in terms of moaning too loudly and too much meant that the pleasure was probably faked.

Mild moans and grunts are much more common, with very little speech, according to the scientists. And, contrary to popular belief, men are just as vocal as women.

'The high-pitched and extravagantly ecstatic screams associated with pornographic films were conspicuous by their absence,' the research paper said.

Researchers from Lund University analysed recordings of 2,239 sexual encounters submitted to them by willing couples. The recordings featured 21,314 sighs, 74,422 syllables, and 54,145 moans or grunts.

One of the aims of the research was to identify any sounds that could be clues to faking it.

'For both men and women, vocalisations became longer, louder, more high-pitched, voiced, and tonal as the excitement peaked,' the psychologists concluded.

'Men are not less vocal overall. Speech or even minimally verbalised exclamations are uncommon. Very few vocalisations could be described as screams.'

Greater volume, excessive vocalising, and length of syllables were signs of a woman faking it, while variation in pitch and the unexpectedness of some sounds were sign of authenticity, the listeners said.

'Based on the observations that women seem to do most of the moaning, human sexual vocalisations are often cast as little more than conscious attempts by women to please their partners,' the researchers said.

'This notion is based on self-reports or pornography studies as no one has yet analysed recordings of actual human sex. This study, the first to perform analyses of authentic sexual episodes, paints a very different picture.

'Based on this new evidence, human sexual vocalisations are at least partly genuine and spontaneous expressions of liking, produced by men and women alike in moments of intense pleasure.'

Men were just as vocal as women, but at different times, they found.

While mild moans from women began slightly earlier in proceedings, men sighed and grunted until the arousal level becomes very high, peaking 15 seconds before climax. This was followed by an average of ten seconds of silence from both men and women. Sex therapist and author Phillip Hodson said: 'This study asks some intriguing questions.

'Sex is an anxious affair about which there is more boasting than business – especially in a world where up to 80 per cent of women claim to have faked a climax, with the same admission from up to a third of all men.

'Loud grunting in bed is no more authentic than loud grunting on Wimbledon's Centre Court.'