I think I found the hole where the animal(s) is(are) getting in. At about noon, there was much noise above my head in the attic. I'm thinking squirrel, bringing in a walnut, dropping it on the sheetrock above my head, rolling it around some...just because it's round. Then twanging some wires. Then running across the floor (my ceiling) and climbing around in the fixtures over the laundry room, picking up small pieces of wood along the way and dropping them. Or maybe it was trying to drag a long stick through the attic and the stick was getting hung up among wires, boards, and detritus along the way.
I couldn't just sit there and not try to do something. So I went into the attics...again. The guys I pay don't seem to be getting the job done. But it's my house and someone has to do it! I wore neoprene gloves this time so I wouldn't quail at going where I knew I needed to go - among the insulation. I went as far toward the slanted-roof edges inside the 2 attics as I could.
I found a tiny hole that has been gnawed in the tippy tip of a bay-window angle way up high in the top attic, but it's very small. Then, in the lower attic, closer to where I have been hearing the activity, I found shavings that look like a nest. This is next to an edge where the slanted roof meets the gutter. When you look from inside the attic, you can't see the whole nest; because the floor of the attic is double, and you can't see the lower part. All I could see of the nest was a few inches of what looks like shavings, but it was enough. I could see a place directly above it on the particle-board ceiling where the gnawing had occurred.
This wouldn't explain all the gnawing sounds like a huge saw that I have been hearing above my office, but it is a start. Because outside, from a ladder, I found a big area right near that attic space where the shingles are easy to lift and the wood is either rotted or gnawed out. I think that's at least one place where animals are passing. The exterminator will be here tomorrow.