If you're running into sound issues, here's what you do:
On your iPad: go to SETTINGS>GENERAL>USE SIDE SWITCH TO
and set it to MUTE.
Then toggle the MUTE switch on the iPad to make sure you are not muted.
Having this function set improperly will not mute your whole iPad (you can still play some Apps and listen to music etc).
You are basically just defining the behavior for the mute toggle on the side of your iPad.
For newer iPad models without a switch, Mute is controlled via Control Center (swipe up from the bottom edge of the iPad) - they are the two icons on the right of the top row of icons :