Reddit mentions of Mindful Discipline: A Loving Approach to Setting Limits and Raising an Emotionally Intelligent Child

Consistent mindful discipline helps even boisterous and rambunctious children learn to control their actions and become better people. This is one of the books I've read, and it's really good.

Inquiry based parenting where you encourage your child to choose to be kind and considerate is a good base. Then you can point out that the speaker is speaking and the other people are listening, and those people can't hear the speaker if you are making noise too. If you raised your child to be a considerate person, they can recognize the effect of their voice on the other listeners around them and quiet themselves. If they start making noise again reminding them "others are trying to listen, please be kind to them" works out worlds better than the stern parenting of "shut up or I'll take you outside and spank you!"

Authoritarian parents are primarily the ones with disruptive kids. Threatening your kids into silence doesn't solve the problem long term. Asking them to think about others does. And they do care about others, and will care about others if you work with them consistently by talking about how their actions affect others.