FreeStyle Libre 3 app includes several types of alarms. These are all turned on by default and initially set to sound regardless of your phone's sound or Do Not Disturb settings. If there's a time where you need quiet, you have a couple of options.
You can choose to silence all your glucose and signal loss alarms for a set period by turning on Silent Mode (if available).

You can individually select to turn off the Override Do Not Disturb setting for the High Glucose, Low Glucose, or Signal Loss Alarm if you want the alarm to follow your phone's volume setting and be silent when you have Do Not Disturb enabled.

Note

The Urgent Low Glucose Alarm can only be silenced by turning on Silent Mode.

Optional Glucose Alarms: Low Glucose and High Glucose Alarms are turned on by default, but can be turned off or customized to alarm at different glucose levels.

Urgent Low Glucose: Urgent Low Glucose Alarm will be delivered when your glucose goes below 55 mg/dL. This alarm cannot be turned off or customized but can be silenced with your other glucose alarms for a set period.

Optional Signal Loss Alarm: Signal Loss Alarm will be delivered when your Sensor isn't communicating with the App. This alarm is turned on by default, but can be turned off or customized.

Fixed System Alarms: Replace Sensor and Sensor Ended Alarms will be delivered when your Sensor needs to be replaced, and the Check Sensor Alarm will be delivered when the Sensor tip may not have been inserted under the skin. These alarms are a little different and will always sound regardless of your phone's sound, Do Not Disturb, or Silent Mode settings. These alarms cannot be modified or turned off and indicate you are no longer receiving glucose readings or glucose alarms.

Note

The iPhone app includes an App Stopped Alarm to indicate you have force closed the App.