Speaking involves so much more than your voice. Hand gestures, body language, stage positioning, and facial expressions all play an important role in making a speech engaging. Let's talk about that last one. Here's an example.

“My sister called and asked if I would pick her up at the airport. At four o'clock in the morning.”

“Sorry, I'm busy.”

It's a funny line, but let's try it with a long pause and the WTF face.

“My sister called and asked if I would pick her up at the airport. At four o'clock in the morning!”

“Sorry babe, I'm busy!”

Try a line like this live and you may have to pause for a very long time while the audience finishes laughing. And that's a good thing. Like I said, speaking involves so much more than your voice. Sometimes it's what you don't say out loud that impacts the audience the most.