Randomly end face time noise from iPhone

So , I have been trying to look this up but I can’t seem to find anything on it.

for the last 2 weeks my phone has been making the noise like when you hang up on FaceTime. I don’t have any new notifications, I don’t have any emails new. My phone is in fact on silent but yet still makes this noise. It happens randomly. Phone can be locked or unlocked. It’s kind of like someone is connecting to my device and the. Disconnecting from it. Does anyone know anything about this ?