Do Not Disturb and Focus Modes: These modes will silence notifications, either globally or for specific times, schedules, or activities.

Do Not Disturb When Do Not Disturb is enabled, your iPhone will stay silent and with its screen off, though there are some exceptions and customizations you should know about.

If they are, the phone will lower the sound of alerts. Apple says on its website that the Do Not Disturb setting and putting the phone on silent does not affect the alarm sounds.