iPad Air 4 alarm keeps sounding every 15 minutes.

The iPad has a clock app. When you open it you will see a plus sign in the upper right-hand corner. At the bottom is World Clock/ Alarm/Stopwatch /Timer. You click on Alarm. Then you click on the plus sign in the upper right-hand corner to set the alarm on or off. The plus sign is how you use the clock app. If you have the clock app you have the plus sign +. So choose Alarm then the plus sign-it’s there and is the function of it. Try it.

Try this: clock app>timer (shown at bottom)> plus sign on top. Here you can choose to shut it off.

You might try Apple Support chat. They are very helpful. Or you could visit the Apple Store for support, if near-by or Best Buy Store-an authorized service provider. Good luck!

Apple Support App.

Maybe delete clock app and then reinstall? Good luck!