S6 edge plus making random tritone sound daily without notification message

[Android Central Question]

My phone makes a random tritone sound several times a day. It started a month and half ago and I've turned off notifications on all my apps. I've also reset to factory settings. I also downloaded an app that tells you what notifications you received but have not been able to determine the source. I'd like to know how to determine the source of the sound.
Thanks

 

[belodion]

Is it a carrier-tied phone? That may be relevant.

 

[Atts6]

Yes it's carrier tied. I purchased the phone from att.

 

[Atts6]

Hi do you have additional suggestions as its carrier tied. Also not a roaming issue.

 

[B. Diddy]

Welcome to Android Central! Does it also happen if you turn off NFC?

 

[Atts6]

NFC is definitely off as is samsung pay. I just turned the phone on in safemode today and it hasn't made a sound. I'll monitor it for the next day or two and if the sounds stop then at least I know it's a third party app.