There are four audible presentation delivery skills:
VOLUME: Talk louder than what you think is appropriate. You never come across as loud as you think.
SPEED: Don't slow down, pause more. The human brain can hear 700 words per minute, but no one speaks that fast. No matter how quickly you speak, never slow down. Instead, pause more. The passion goes out of your voice when you slow down. And you need to give your audience thinking time to digest what you've said.
ANIMATION: The tonal fluctuation in your voice gives your voice passion and interest. It gives people the impression that you truly believe in what you’re talking about. Our voices tend to flatten out and drop down when we're nervous or when we're saying something serious. Our voices become a monotone. And we perceive monotone voice sounds as dull, boring, and generally not as worthy of our attention.
NON-WORDS: Avoid verbal fillers in between thoughts. As speakers, we tend to get nervous about silence. Often when we lose our spot or at the end of sentences, we feel like we must add in a non-sensical sound (or a real word like “and”). By tying together thought after thought with constant sound, we rob our audience of time to digest what we're saying and sound less authoritative on the subject matter.