what chirps like a cricket?

Yesterday, I thought I would go crazy. I kept hearing a chirping noise in my house. I was in the basement and immediately thought of crickets, which tend to come inside in the fall. We once had a cricket that chirped almost all winter before we found it. I even checked the chirp smoke detector, but all of them are run off the house electricity, so it couldn't chirp be that. Didn't find any crickets and anyway the chirp noise seemed to be from upstairs. Ok, I'm in the living room and chirp I still hear it. I get a stool, climb up and take the cover off the smoke detector. Don't see any batteries, just chirp wires. Maybe there is something wrong with the thermostat which is chirp on the wall in the same part of the living room. It seems ok, and actually the heat/cooling system isn't running now as chirp the temperatures are lovely outside so I don't need either heat or A/C. I finally decide it must be the smoke detector chirp. The sound is driving me crazy. I turn up the radio and hear lovely classical music interspersed with chirp. HELP! I can't escape. In desperation, I took some styrofoam and cut it to make a box enclosing the chirp smoke detector. Praise God for duct tape! It's better now. I hear chirp a much softer sound, but it's still there. I wonder if I'll have to call an electrician and pay $60 an hour to get this problem chirp fixed. Then I have a thought - I'll ask a neighbor. One good thing about living in a townhouse is that we all tend to have the same problems chirp at about the same time. (Everybody's heat pumps had to be replaced a year or two ago; everybody had to get rotted wood replaced in the front.) chirp I go next door and in their ceiling is a smoke detector hanging from its wiring. Somehow I have no trouble guessing why. But it is NOT chirping. Sure enough, they have had the same problem and yes there is a battery (for backup purposes) in the smoke detector. My very helpful, very tall neighbor comes over to my house, reaches up and removes the cover to the chirp smoke detector. He then disconnects it and pulls out a 9 volt battery. The smoke detector is in his hand and it says chirp! I put the darn thing in the basement where I cannot hear it chirp and go to buy a new battery. Put it in and all is quiet. Thank goodness.