When parked up with the engine idling, my climate / aircon system really gurgles - is this normal?

Never had this on the Audi nor Octavia and just wondered whether all was well. The system works fine as it should.

I've heard it on some cars before. On those cars it was because the gas was a bit low. My previous Superb didn't do it though, but it was only a few months old when they took it away from me.