Croatian Heartbeat
The sound the formation of dry ice makes in the chest cavity of a Croatian person. Dry ice replaces the standard human heart if you are of Croatian descent.
Doctor - "My God, you have the strangest heartbeat I've ever heard!"
Patient - "No, I'm just Croatian. What you're hearing is actually a standard Croatian heartbeat."
Patient - "No, I'm just Croatian. What you're hearing is actually a standard Croatian heartbeat."