And wouldn't you know -- around Halloween time!

This is a kind of croaking, grunting, or grumbling sound coming from from a fairly specific place in the wall of an upstairs room in an older two-story wood frame house.

I've pretty much eliminated wind, passing traffic, and other external sources. It's intermittent, not regular timing, and often absent for several hours at a time.

I think insects would be continuous, so if it's alive, I would guess a squirrel or a mouse. We've had mice, but they usually sound like they're busy scurrying about, not hanging out and grunting.

It sounds like a metal ornament or gutter drain rubbing against the house in the wind -- however, as I've said, I'm almost certain it isn't external to the house.

d-CON pellets have worked with mice before, so I've placed them in the attic.

Any idea what would cause this type of noise? Thanks!

From what I've discovered so far, the description fits "carpenter bees" although I've never heard of them before, and to my knowledge they're not a common pest here (in New England).

We've had carpenter ants, but those are something quite different, and they were (so far) completely eliminated by a pest control company.

Any comments would be appreciated. I plan to call the pro's tomorrow.