As a retired teacher this works the best. Stop talking and look directly at the those who are disturbing the meeting. When you have their attention ask if there is something they'd like to contribute and then remind people to ask questions after the talk. Speakers are usually freebies for a club. They should be treated with respect. Not everyone is a strong speaker so shouldn't be expected to talk over those rude enough to disturb a meeting. As a teacher I seldom raised my voice yet my class was always quiet and respectful of others. In contrast a teacher across the hall was always shouting and her children shouted along with her!