Что это?

A visual representation of different dynamics.

Где его найти?

DIY and bring it with you.

Как мне его использовать?

Move an arrow or other visual indicator to show students where they should be on the dynamic scale. If possible, correlate it to language about volume that they already know (e.g., a class might use a number or color system to indicate quiet voices, speaking for a large group, etc).