(boolean or undefined)
The critical alert flag. Set to
true to enable the critical alert.
(string or undefined)
The name of a sound file in the app's main bundle or in the
Library/Sounds folder of the app's container directory. Specify the string "default" to play the system sound.
(number or undefined)
The volume for the critical alert's sound. Must be a value between 0.0 (silent) and 1.0 (full volume).