Rosa

Trying to find out what this chirping sound is. I Hear it at night and it sounds like a smoke detector with low battery. It's coming from outside my home; from a tree? the sky? I've heard it before in my previous home. I can't find the source and it's a bit unnerving. It is not a cricket or crickets, sounds more mechanical, every two minutes or so, I hear that chirp. Is that silly? Has anyone heard anything like that? It goes on for hours.