Every administrator, teacher, parent, and student has different levels of tolerance when it comes to sound levels.  Some classrooms I work in can be eerily silent, or too loud for me to think, let alone the students.  The fact is, noise can have an affect on student productivity and learning.  To get more of the science behind this, there is a great article discussing a research study done inside classroom at blog.sparkypro.com.

There are some ways that we can help control this level for the entire class and for individual students.

For the entire class, it can be useful to explicitly teach the students what the expected sound level should be for different activities.

The full version with description is available here:

Classroom Noise Meter

This visual is used to set expectations before and activity and silently prompt a reminder to the students.  In my room I have this printed and on the white board with an arrow to the present noise level.

For individual students, this could be made smaller and placed on their desk.

This is just one of many ways to set expectations or make accommodations for noise levels within the classroom.