We’ve had good luck asking them to be quiet for a period (eg 2 minutes) and then rewarding them. Can be repeated, but also often breaks the noise cycle. And sometimes depending on age and mood just asking works.

For reward, we use a pom pom jar. Single quart jar shared by all kids. They select what they are working towards when they start a new one. Takes about a week for them to fill it and get ice cream or pizza or sleepover or whatever.

Parents have to notice and reward - they are not allowed to ask for pom poms. Eliminates nagging. But it also serves as a reminder for us to actively notice good behavior rather than just focusing on poor behavior.