You know when you are in a classroom and everyone is being loud and the teacher wants to talk? The teacher might raise their hand and say "quiet down" and wait for everyone to stop talking before they start speaking. This is called a "silence procedure."
In some places like a courthouse or a council meeting, when people are discussing important things, they will also use a silence procedure. Instead of just raising their hand, they might actually ring a bell or use a microphone to ask for everyone to be quiet before they start talking.
This is important because when people are talking and making noise, it can be hard to hear and understand what someone else is saying. When everyone is quiet, it helps make sure that everyone can hear and understand what is being said. This is a way to make sure that everyone can be heard and understood when important things are being discussed.