I found this an interesting study.

http://www.ctv.ca/servlet/ArticleNews/stor...25?hub=CanadaAM

article below

Men with deep voices have more kids, study finds
Updated Tue. Sep. 25 2007 8:13 AM ET
The Canadian Press
TORONTO -- Men, how low can you go?
Your voice, that is.

As you hear yourself answer the question aloud, does the response come out Pee Wee Herman-squeaky or Barry White baritone smooth?
Studies suggest the pitch level of a man's voice could have an impact on his appeal to the opposite sex, with new research indicating women wanting to have children may favour a mate with more huskiness in his speech.
In previous studies conducted by a team of researchers, including McMaster University professor David Feinberg, women were shown to find men with deeper voices to be more attractive, deeming them more dominant, older, healthier and more masculine-sounding.

This was determined after subjects heard voices in which the pitch had been manipulated and had to rate them on a scale of what was judged as most and least attractive.

On the flipside, men judged women with higher-pitched voices to be more attractive, subordinate, feminine, healthier and younger-sounding.
Yet a more recent study found men with lower voices had greater reproductive success and more children born to them, Feinberg said.
Feinberg and his colleague, Coren Apicella, an anthropology graduate student at Harvard University, selected members of the Hadza of Tanzania as subjects for the new study, to be published in Biology Letters on Wednesday. The tribe is among the last remaining hunter-gatherer cultures and has no modern birth control. The men were asked how many children they had had, both living and deceased.

Apicella and Feinberg later listened to the recordings run through a computer algorithm to detect voice pitch, measuring the results against another set of numbers tracking reproductive success for the entire group.
"What we noticed was that men with lower-pitched voices tended to have more babies than men with higher-pitched voices did, and we thought, `OK, is this because men with higher-pitched voices, their babies aren't really surviving, or is it because men with lower-pitched voices are having more babies?''' said Feinberg, an assistant professor in psychology, neuroscience and behaviour at McMaster in Hamilton.

It's more likely men with lower-pitched voices can find more women than their high-pitched counterparts, rather than the possibility that men with higher-pitched voices are having their children die at younger ages, the findings suggest.

Pitch level is measured in hertz (Hz), a measurement of fundamental frequency of the voice, how many cycles per second the sound wave has in it, Feinberg said. While decibels are measured relative to a reference noise, hertz is an absolute scale, like Celsius, he added.

Feinberg said the average man's voice is at 120 Hz, and ranges from 90-160, while women's voices are a full octave higher, ranging from 180-280 Hz. Babies are generally in the 300-500 Hz range.

The findings don't imply that voice pitch is a determining factor in how many children you'll have, Feinberg said.

"We just correlate the number of children you have with the voice pitch,'' he said. "We won't know, say, 100 Hz means five babies, 160 Hz means one baby.''

"It's not that there's a sort of absolute number that predicts an absolute voice frequency that predicts how many children you're going to have. It's more likely that within a certain range, men with lower-pitched voices on average are going to have more babies than men with higher-pitched voices will.''
Feinberg said if ancestors went through a similar process, it could count as one reason for the differences in men's and women's voices.