Male lawyers who sound very masculine are less likely to win a US Supreme Court case than their more gentle-sounding peers, a new study has found.

A team led by linguist Alan Yu of the University of Chicago and legal theorist Daniel Chen of ETH Zurich in Switzerland set out to explore whether the vocal characteristics of male lawyers affect trial outcomes.

The researchers collected 60 recordings of male lawyers in the US Supreme Court making the traditional opening statement: "Mister Chief Justice, may it please the court".

Then 200 volunteers rated these clips for how masculine they thought the speaker was, as well as how attractive, confident, intelligent, trustworthy and educated they perceived the voice to be.

Researchers found that lawyers rated as speaking with less-masculine voices were more likely to win, 'New Scientist' reported.

Yu now wants to explore whether the perceived likelihood of winning affects how lawyers speak.

"Lawyers who think they're going to lose may project a different kind of voice, perhaps overcompensating by sounding more masculine," Yu said.