You can do this by listening to your sound through headphones or speakers and checking for any issues like static, hissing, popping, or crackling. You can also ask someone else to listen and give you their opinion.

Pairing the Status Between 3ANC is simple given they turn on in pairing mode the first time you open the case and take them out. Indeed, the case is specifically designed to push the physical buttons down and turn off the IEMs when stored, meaning they simply turn on and go into pairing mode when removed.