For you kindergarten students to maintain proper noise levels in the classroom, they need to know what those noise levels are. Verbally demonstrate the noise level that is appropriate for each activity. For example, noise levels will be different when students are working independently than when they are working pairs or groups. Display a chart in the classroom that you can use to mark what noise level is appropriate for the current activity.
You need to get your students' attention when the noise level starts to rise in the classroom. Yelling over your students is rarely effective, but ringing a bell can often get them to quiet down enough for you to talk to them. A simple clapping rhythm is also useful. Clap four or five times in a specific pattern and teach your students that whenever they hear that clap, they need to stop what they are doing and repeat the clap. This not only gets your students' attention, but also redirects their behavior.
You can also alert your students to the fact that noise level in the classroom is too high using visual cues. Raising your hand or showing a peace sign lets children know that they are too loud and gives them the opportunity to manage their own noise levels. If that does not get your students' attention, try turning off the light for a few seconds.
Allowing your students to police their own noise levels can be extremely effective. If a student notices that the noise level is too high, she can raise her hand to remind her classmates of the proper noise level. As other students take notice, they should remain quiet and raise their hands as well. Reward students with praise or stickers when they maintain proper noise levels in the classroom.