Mice (or rats) in the walls dragging plastic around for bedding?
Worth mentioning, for sure - though I don't think it was anything quite like that. I've lived in places with both mice and rats active (yeah, I'm pretty classy) and never heard anything resembling such a noise that I could attribute to rodent activity.
The snapping noise sounded exactly like the noise you'd get if you stretched your arm out, and snapped your fingers (your volume may of course vary, but I can snap 'em quite loudly).
But it also sounded
close if you get me - like the noise was being generated less than a metre from my head. Not anything behind the wall, or under the floor, or in any way muffled. Very clear, very sharp. Very close. Snap. Snap. Snap. Snap. Snap.
The room was very, very large; too big for a bedroom really - it was the former first floor drawing room of what had once been a very grand house built around 1800. The walls were solid, not cavity, and while the property did of course have its quota of odd noises, this wasn't one I recognised - or ever heard repeated during my time there.
And the directionality went around me - if I'd just heard some snapping, I might have assumed there were birds roosting in the chimney stack, as there was a huge marble fireplace in the room that might well have amplified any noises.
But I sat bolt upright, fully awake, and still the noise kept sounding around me, seemingly close, and going from side to side like one of those 'New Adventures In Stereo' LPs, where the sound would pan from one channel to the other and back again.
It probably went on for about thirty seconds, all told. Never experienced anything like it before or since.