I went to put some wood on the fire, and when I opened the door, I heard ... howling. For a moment I wondered if it might be just sap boiling and squealing, as it sometimes does. But not, this was quite clearly coyote howling. From the woodstove. It wasn't audible anywhere else.
It only took me a couple seconds to realize that it was coming down the chimney, which connects to the outdoors, where there are coyote packs howling. The pipe catches and magnifies the sound.