Gena, a recent visitor to this website, posed the following question:

I always keep the sound button on both my iPhone 6 and iPad 2 turned off at night when I got to sleep (the button on the side of the device). If an email or notification comes in, the device vibrates but does not ding. During the last several nights, however, I’ve been awakened by one ding each night from the iPad. (The iPhone is still silent.) Do you have any idea why this might be? I’ve read here and elsewhere about going into settings and changing things, but isn’t this a defect in the way the iPad should work? Is it because it’s old and pretty full?

Thanks for any insights you may have.

Gena is talking about the Side Switch on her iPad, found just above the volume control. The Side Switch can be found on most iPad models, including the first. The new iPad Air 2 doesn’t have a side switch. The switch can be set to mute sounds or to lock rotation.

When you use the side switch to mute your iPad, you won’t hear these sounds:
Alerts
Notifications
Sound effects
Game audio

You’ll still hear sound from your media, including:
Music
Podcasts
Movies
Videos
TV shows

I believe an app is making this mysterious sound. Most likely the sound is set to “Note” or “Ding” for the app. Sounds for native apps are controlled in Settings > Sounds. Sounds for apps you installed are controlled in Notifications. If you go to Settings > Notifications, you can see what apps are configured for sound.

The default email delivery sound is a ding noise. The mystery sound may be an email message coming in. Check your VIP email list and see if any time stamp matches the nighttime interruption. You may have set a contact to VIP, which overrides the side switch and tells you a VIP email has arrived.