As per title, really, was travelling to ACE last Sunday on an A320 (G-MEDK to be precise). A couple of hours into the flight, there were three low 'bongs' over the tannoy - deeper and louder than the usual bing-bongs. I may just have never noticed, but I don't recall hearing it before now.

It sounded like some kind of alarm, and indeed, the purser's face seemed momentarily to be somewhere between confusion and concern. She interrupted her drinks service and went back behind the curtain, quickly followed by the other crew member serving CE. I couldn't see what happened next, but a few minutes later, both returned to CE and spoke to one of the flight deck who had come out of the cockpit (though this may have been coincidence). Normal service resumed, and I had another bottle of Monopole (which, by the time you're on your third, isn't actually that bad!).

Any thoughts what this might have been?