iPhone playing weird church sound randomly

Hey.
I've noticed that my iPhone plays a weird church bell like sound just randomly maybe 2-4 times a day.
It's almost like a clock that would hit say 6 o'clock and play sound, you know what I mean?

But it's weird because it plays it just randomly, even if the clock was 5:34 or something, I've checked all programs and none of them have any notifications when this occurs.

Any ideas?