No, it was the lovely and talented Flight Attendants, chatting in the galley. It may also have been said FAs banging and slamming various doors and panels as they chatted.

I know it is definitely tough to get to sleep on a plane. However, that is why I always bring my Shures which are not only earphones but earplugs as well. I also bring a Brookstone eye shade (expensive but well worth it!). Then , when I am ready to go to bed, I pop in the Shures and if I wish attach them to my MP3 player for low relaxing music, and put on the shades, which block out all ambient light. I don't hear or see anyone.

I think the problem here is that not all people want to do what I want to do late at night (or even not that late). Some want to watch movies, others read, and some talk. I cannot stop them from doing this because I want to sleep. Could the FA's be quieter... sure, but they have to work while I am sleeping. So, my suggestion is get earplugs and eyeshades and sleep without interruption.