We have 2 Maple Chase 7 days programmable thermostats. One upstairs and down. Just recently, the one upstairs started making this funny 'chirping/vibrating' noise. The thermostat still works (it heats the house), but the noise is sort of annoying... I replaced the batteries, even though there were no 'low battery' message on the display window, and even RESET the system. The noise is intermittent. I looked at the fuse, and that seemed okay as well.

"Future Shoes" by Michael Finley (http://www.skypoint.com/members/mfinley/articles/noise.htm)

Look around for a smoke detector that needs a battery change.