Ivan,
I just love the idea of a baby monitor in the house! I'm SOOOOO copying that!
I have 5 BR that coo and make all sorts of noises (too new to know what's normal) but one makes her own set of noises particularly when she's being held- the closest I can come to describing it is clean fingers rubbing a wet wine glass. Like she's cleaning windows! Very distinctly different from the others...George is a weird one, though, probably to do with the kids giving her a boy name...