Topic 1: novice public speakers make those sounds because they draw their learning and experience from conversation. In a conversation, you're taking turns, and

Topic 1: novice public speakers make those sounds because they draw their learning and experience from conversation. In a conversation, you're taking turns, and doing some noise is the signal that you're not yielding your turn yet. When speaking in public, at least in the context of a civilized presentation, you don't need it, because the audience has tacitly agreed to just listen to you, but your conversational habits are so ingrained that you still apply them by sheer habit. Topic 2: the reason you can't concentrate on what you're saying is that a group paying attention to what you're saying is a threatening situation, and you are in alert mode, probably adrenaline and other related signals high in your bloodstream. It's pretty hard to concentrate in your thoughts about whatever rational topic while you're body is telling you every way it can that you are in danger. You can't speak well in public until you stop feeling in danger, and the best way to get there is to do it a lot. Maybe you are in danger, because a large number of people's judgement of you may be swayed with just one sentence you said, but you just need to get accustomed to a higher-stakes game (or drop it, you don't have to, but that's what it is). Source: developer who's been programming for 30 years and who's done a ton of stand-up comedy in the last 5. Nothing like that to really become good at public speaking...