How to — Literally — Sound More Confident and Persuasive – The New York Times

“Every time we interact with someone, we’re trying to figure out how much they know about what they’re saying, how knowledgeable they are, how confident they seem,” said Jonah Berger, an associate professor of marketing at Wharton and a co-author of the study. “We found that these cues in particular” — the ones related to speaking volume — “made speakers seem more confident, which made them more persuasive overall.”

NY Times