Anyone else have this problem?
Yes, had this happen too. Weird.
BTW - I figured it out!!
I realized the sound was happening every time my cover was "open" and my bank cards were behind the phone. Realized my NFC had been on the whole time. So it kept trying to read my cards, and that is where the sound came from!
I have now turned NFC off and the sound has not come back. What a relief!
I had another phantom alert ping this morning. Nothing to do with NFC in my case.
Could it be an application sending out notification beeps in background, but the notifications are blocked from displaying on homescreen?
Try switching off NFC as mentioned in the previous replies and Changing the notification sound of the applications to narrow down the application making the beep sound.
1 Check Settings > Sound > Other Sounds > Screen Locking Sounds.
This is the sound during phone lock / unlock. This should be OFF.
(This sound is like a cap being opened from a soda bottle , like a pop sound)
You can instantly check this by Locking / Unlocking your phone !
2 Switch off NFC.
3 IF you are using social applications , like WhatsApp. You could be getting notification sounds in groups. I.E. If you are mentioned in the chat. And various other possibilities. So Change the Tune of the notifications and you can narrow down which app is making the noise in the background !!
And it may not be showing notifications, so check those settings as well.
I still suspect an application making this noise on your phone. No one is mentioning about such issue and according to this post it was identified as NFC / Lock sound.
If u can give more info about the sound , it can be helpful actually. When does it occur, how frequent?