hmm, this seems difficult to describe, I've been searching for audio sounds and videos of something, I haven't found a anything. It's not a queen piping, hissing, humming and so on. It sounded more like the bees in the hive were chirping an organized, orchestrated song, I was on my second pass through the frames, had heard it, paying no attention to it then it struck me. I looked inside but couldn't figure out what it was about. It wasn't constant it would stop and start.
The link about the warble describes some of the same behavior best. Maybe I ought to look for a swarm that took off in the area. That crossed my mind when I first heard it but I wasn't sure. Why would a 5 frame nuc installed in a 10 frame deep, 3 weeks old swarm so soon? Perhaps it was the pierco frames around the wood frames or some other reason.