I taught Kindergarten for over 25 years, and I know how difficult it can be teach young children how to be quiet and control their noise levels. Developmentally, students that age are not ready to be quiet for long periods of time, so it’s important to alternate active/noisy times with quiet ones. They need a chance to let loose. This can be done with something like a quick song or 2 that includes movement. Just be sure that any method you try gets an ample opportunity to work for you. Nothing works right away.
Here is one activity that worked well for me. Write a scripted story about being quiet. It can be something like this: “When I talk too loudly, I cannot hear Mrs. ____. I miss fun stuff. It hurts my friends' ears. I need to turn down my volume button. When I talk softly, I don't miss anything! Everyone is happy and I have fun.”
Use clip art to illustrate. Put the book in page protectors or laminate it. Read it daily before the problem occurs, and read it again as needed, when the problem occurs. The more you read it, the more effective it will be. At some point you can cut back on the readings. You may even reach a point that you can just hold up the book as a signal/reminder.