Notification settings are relatively complex on a modern iPhone or iPad. An application can make sounds or vibrate your phone without displaying visible notifications. Here's how to identify the offender.
Ghost vibrations (and sounds)
It should be remembered that ghost vibrations are a common phenomenon. Many people have felt their iPhone vibrate in their pocket, only to take it out and realize that it had not vibrated at all. Ghost sounds can also occur, especially in noisy places. Did your phone notification really play? Maybe it was just another sound in the middle of the din, or the same notification sound coming from someone else's phone.
But that's not the only problem. Your iPhone may have vibrated or sounded even if there is no notification on your notification center or on your lock screen when you check it.
An application has invisible notifications playing sounds
Apps can have invisible notifications that make your phone vibrate or play the sound of your notifications.
To check this, go to Settings> Notifications. If an application is set to "Sounds" without "Banners", it will emit a notification sound without displaying any visible notifications. If an app is set to "Sounds" without a banner, but with "Badges", a red notification badge will be displayed with a counter of new items on the app. It sounds a sound when the badge increases, but it does not show any visible notification.
Scroll through the list and look for such sneaky apps. If you see one or more items set only to "Sounds", they are probably causing the beep and mysterious vibrations of your iPhone.
If you find such an application, tap on it, then choose what you want to do. For example, you may want to completely disable notifications for this app by selecting "Allow notifications" or by enabling visible notification banners under "Alerts".
A notification appeared and disappeared
Your phone may be ringing and waking up only for the notification to disappear a few moments later.
It's not very common, but it happens. The same app that sent a notification to your phone can "un-send" it and delete it from your phone later. You can see it in action when you use messaging applications on multiple platforms. If you view an unread message on another device, the application often erases notification of that message on your iPhone. After all, you've already seen it on another platform; you do not need to see him again.
Some email applications may also allow someone to delete a message that has been sent to you. Depending on the way the email service is scheduled, the app can also clear the notification from your iPhone or iPad. In other words, if someone sends you a message and deletes it, your iPhone may beep or sound, but the notification may disappear before you look at it.
Again, this is not very common – even some applications that allow users to delete messages do not automatically delete the notification associated with the message. There is a good chance that the vibration in your pocket is simply a ghost vibration and not associated with a notification that has since disappeared.
On an Android phone, it is possible to look at the history of notifications to determine if this has happened and see the text of the notification. However, Apple's iOS operating system does not offer such functionality. On an iPhone, there is no way to know which app sends and clears notifications unless you look at the screen when the notification appears and then disappears.