How do I make my Apple ID sign in request silent?
The two-factor authentication alert follows the volume of Ringer and Alerts. It can be adjusted via the hardware volume buttons, although you may have disabled that functionality.

If that is the case, head into Settings → Sounds and adjust the slider for Ringer and Alerts. This will affect the volume of all notifications (including FaceTime call notifications).

If you want to completely silence those alerts, you can:


Drag the slider all the way down.
Use your iPad’s hardware mute switch (removed starting with iPad Air 2, iPad mini 4, iPad Pro and iPad 5).
Pull up the Control Center and enable the crossed-out bell icon.