Remember it is your show. You are in command. If people start talking among themselves while you are presenting, STOP! Politely ask them whether they have a question or if they need a break. Don’t try and compete. Get them to focus on you.
If there is any kind of distraction in the room that is bothering you, it is probably bothering your audience too. My favorite is the assistant who comes into the room in the middle of a presentation and sidles down the side of the room to hand a phone message to someone. No matter how quietly or unobtrusively they enter the room, the audience will follow them around the room. The focus is no longer on the presenter. Stop and let them deliver the message. Don’t try to compete.
Eliminate a potential problem by waiting until the focus can get back on you and your “show”. Just as a nightclub comedian has to learn how to handle hecklers, you must learn how to handle “distracters”. It takes practice, patience, and self-confidence, but you can do it.