Booming voice ... new Foreign Minister and Senator Bob Carr is known for his deep tones.

Booming voice ... new Foreign Minister and Senator Bob Carr is known for his deep tones. Photo: Alex Ellinghausen

A deep voice may be one of Bob Carr's best weapons in his new role as Senator and Foreign Minister.

But Opposition education spokesman Christopher Pyne's higher tones could make it harder for him to connect with voters, according to a new study.

US researchers have found that voters prefer political candidates with low-pitched voices.

High-pitched battle ... Anthony Albanese and Christopher Pyne talk on the floor of Parliament.

High-pitched battle ... Anthony Albanese and Christopher Pyne talk on the floor of Parliament. Photo: Andrew Meares

Duke University biologist Susan Peters and and University of Miami political scientist Casey Klofstad recorded men and women saying "I urge you to vote for me this November," and then edited the recordings to create higher and lower pitched version of the original.

The recordings of the female voices were played to 37 men and 46 women at the University of Miami and the male voices to 49 men and 40 women at Duke.

The candidates with lower-pitched voices subsequently won mock elections.

"Among women, the preference for lower-pitched male voices could be because women find men with lower voices to be more attractive, a perception that can enhance a candidate's electability," the authors wrote in the Proceedings of the Royal Society B: Bio-logical Sciences.

"Among men, lower-pitched male voices are perceived to be stronger and more competent, attributes that are likely correlated with perceptions of leadership capacity (and especially so within the context of male–male competition)."

Lower-pitched politicians in Federal Parliament include Mr Carr, Nationals Leader Warren Truss and Finance Minister Penny Wong.

Mr Pyne and Transport Minister Anthony Albanese have higher voices in debate.

Prime Minister Julia Gillard and Opposition Leader Tony Abbott have middle-pitched voices.

The study's authors said the findings could also help explain why women were under-represented in political office across the globe.

"While gender discrimination is an obvious cause of the under-representation of women as leaders, our results suggest that biological differences between the sexes, and our responses to those differences, could potentially be an additional factor to consider.

"More specifically, because women, on average, have higher pitched voices than men, and because higher-pitched female voices are judged to be weaker, less competent and less trustworthy, the characteristics of this vocal signal could help explain why women are less likely to hold leadership roles than men.

"At the very least, voice pitch is a physical characteristic that does not counterbalance social norms that foster gender inequality."