This was the case when Clinton spoke to a United Nations commission and when Sanders spoke to the U.S. Senate. Sound is a vibration, or wave, that moves through matter and can be heard. Some of the most successful politicians are outstanding speakers, and with good reason. "Politicians use voice as a very powerful behavior to convey their charisma," Rosario Signorello said. A paragraph on chopped carrots might sound boring in a dull speaker's voice but riveting when recited by a Shakespearean actor. Politicians may share some speech tactics for impressing an audience, but they don't behave exactly the same. Their success is not only due to the words they choose. Signorello and his fellow researchers have found that this strategy helps speakers to be seen as charismatic and likable. The candidates try to match each group's idea of what a charismatic leader should sound like, he said. When it comes to politics, it's not what you say, it's how you say it. This tactic makes sense for this type of audience, Signorello said. Low and medium frequency pitch patterns are meant to signal power and dominance. Signorello said that politicians are the best public speakers because they face every type of audience, addressing everyone from elementary school students to very old people. General audiences include a variety of people. Seasoned politicians know this very well, but this year's unsuccessful presidential hopefuls may have learned it the hard way.