Since I usually have a portfolio or some similar notebook with me and I know the people who act like this; I just keep scribbling stuff in my thing and act like I wasn't listening or maybe passively listening, so then I can just be like "I'm sorry, what was that?"

If you make jerks repeat something out loud it throws off their rhythm. If they bother to repeat it, then you can just say "oh ok, cool" and turn back to your scribbles.