Some squeak, some purr, and some grate, but however they sound, voices often speak louder than words. What can you get from a phone conversation's introductory "Hello"? PT moves beyond mere semantics.

People with bilaterally balanced bodies have voices that are rated more attractive. According to Gordon Gallup Jr., professor of psychology at the State University at Albany, "Voice is, in effect, a medium for the transmission of biological information."

People can estimate a speaker's height, weight, and age from his voice as accurately as they can after viewing his photo.

When men are in the presence of someone they deem less physically dominant, they assert themselves and their voices drop in pitch. However, when intimidated, their voices go up.

Want to know how sexually promiscuous someone is? People with attractive voices have had more sexual partners and report an earlier age of first sexual encounter. They're also more likely to cheat.

Malpractice has a certain ring to it. Subjects in a Harvard study identified surgeons who had been sued for malpractice after listening to their voices for 40 seconds. The most litigated doctors tended to share voices that were dominant: "deep, loud, moderately fast, unaccented, and clearly articulated."

What separates the voices of Don Juans from those of average Joes? Men who score with women can more flexibly modify aspects of their voices like pitch and volume throughout a flirt session—opening up with a dynamic, loud voice and later becoming softer and more monotone to suggest tenderness.