Ghost Notification Sound, Need Help

[marlap2000]

It's not an app and it's spamming the default notification sound. It lights up my screen when the phone is on mute and it happens a few times per minute. I need help figuring out what is causing this noise. I have the Verizon S7 Edge and I've tried stopping all sorts of running apps using developer options and I turned off all notifications in settings and it still keeps happening. Does anybody know what can be making this battery draining and annoying ghost sound?

 

[B. Diddy]

Is NFC on? If so, make sure there isn't anything with an NFC chip (like a credit card) right near the phone. This can happen if you have the phone in a wallet-style case, and have credit cards in the wallet that contain NFC chips.