FIX: This problem can be fixed if you just do a complete new fresh restore on your iPad. You CAN NOT restore from a back up which will bring the sound issue back. It probably has to do with corruption data being stored within the backup. Just do a fresh restore without backing it up. You will have to start over but just log onto your iCloud account and you should be able to restore contacts/notes/email and etc. But you will have to redownload the apps.
Note: There are a few times I plugged the iPad Mini to my surround sound system so it can be heard more clearer.