iPhone X I making random chirping noises

dor the past few months I have been hearing this random quick double chirping, I could never locate it and it always happened at work so I never knew what it was coming from until tonight when I was on my phone and heard it finally coming from my phones ear piece speaker while I was in an app. All the other times the chirp came while the phone was in my pocket and when I suspected it was my phone, there was never anything displayed in the screen. Even just now when it happened nothing showed on the screen even though I was looking directly at the phone. (iPhone X) so I was hoping someone might have some clue what the noise might be. I have already tried googling but none of the other reports sound close to my issue.

it is two quick chirps, it happens maybe two three times a month so always at different times so it is hard to pinpoint if any app might be causing an issue.

Unlike all the other things I find in google, it is NOT a loud fire alarm noise, it is NOT the charging ping sound, it is NOT the Siri double beep. It’s just two quick, high pitched chirps I have never heard in any IOS device before. It’s loud enough for other people to hear it in my pocket as well as me, but doesn’t happen often enough to pinpoint whether or not it is from an app. Does anyone have any ideas? iOS is 11.3 and it’s not any interaction between any of my Bluetooth or smart devices because it usually happens at work, today was the first time it happened at home . Thanks for anyone that can help.