Washington:  Women often find deep-voiced men more attractive, but a new study says such men are not always better in one of the masculine traits: virility.

Researchers from the University of Western Australia found that though men with a low-pitched voice are considered more muscular and attractive, they don't have "macho" sperm.

The first finding of the researchers, who looked at male voice pitch, women's perceptions of it and semen quality, was no surprise: Women like low-pitched voices and consider them masculine.
But contrary to expectations, they also found that these aren't better off in the semen department. In fact, by one measure of sperm quality -- concentration -- men with the deep voices appeared to have a disadvantage, LiveScience reported.

This is a surprise because females, both humans and of other species, are believed to glean information about male virility through secondary sexual traits, such as facial hair and muscle mass in humans and other traits in other animals, such as colourful plumage in birds, the researchers said.

In the case of voice pitch, the researchers suggest there may be a trade-off at work. In other words, traits associated with dominance and attractiveness, such as physical strength a deep voice, may come at the cost of reduced sperm quality, the researchers said.

For instance, higher testosterone levels are associated with a deeper voice, more masculine features, more dominant behaviour and success in obtaining sexual partners.

Although testosterone plays an important role in the formation of sperm, however, high levels of it can actually impair sperm production, the researchers wrote.

For the study, published in the journal PLoS ONE, the researchers recruited 54 men to provide voice recordings and semen samples. Their recordings were analysed by software and ranked by 30 female volunteers on attractiveness or masculinity.