London, Oct 8 : Women speak with a squeakier voice at the time of the month when they're most fertile - making them more attractive to the men, scientists have found.
The finding implies that a high-pitched voice - not a husky one - may be the key to finding a perfect mate.
Previous research found men pick up on other, less subtle clues to a woman's fertility, such as scent and flirtatious behaviour.
There is increasing evidence that women's behaviour changes in subtle ways throughout the monthly cycle, and that men find women most attractive around the time of ovulation.
A study last year found that the earnings of lap dancers increased dramatically when they were most fertile.
In the latest study, America researchers followed 69 women for a month, using fertility tests to show when each was most and least likely to become pregnant. Voices were taped to discover the pitch and speed at which they talked.
The University of California team found that at the most fertile times of the month voice pitch rose, peaking in the two days before ovulation was due to take place.
The study has been published in the journal Biology Letters.
The study's researcher Gregory Bryant, from the Department of Communication Studies, Center for Behaviour, Evolution and Culture, said the women sub-consciously added pitch when speaking to others.
"This raises the intriguing possibility that cues of ovulation appear during social interactions and could serve a communicative function," the Daily Express quoted him, as saying.