Does your sump pump, water meter or anything else have a battery backup? At an old house, I had a gas meter in the basement that would softly chirp (or squeak) when the furnace kicked in, making the dial turn.
Sump pump backup is water-powered w/ no alarm; nothing like that for the gas meter; the FIOS backup system (for internet telephone service, for our 1 wired handset) is in the green. I think I just heard it, and believe it's one of those 'enhanced' cat-toys --- squeeks/chirps like a small creature of prey; getting a flashlight to further investigate <g>
My god man, do *NOT* go into that basement with a flashlight looking for the source of a strange noise. Haven't you seen any movies?!?
OMG! Purr-fect if it's a cat toy! Those damn things are always getting lost and the fact that one of them might have a "homing device" feature built in is incredibly - wait, what's the word? - (Evil) Genius! Your cat can now drive you insane and it doesn't even have to be awake - or alive - anymore to do so. Hook , he's been gone a pretty long time, don't you think?
Even better, Lauren, to read your and Hook's post w/ Sophie on lap for the record, the flashlight was to check under the tv cabinet, to better count how many toys (by design and otherwise) there were
That remains to be seen, I guess. Wife insists not a cat toy making noise, that it *definitely* was from the basement (no cat toys there)…the definite good news, though, is all our CO detectors have fresh batteries
Other beeping theories: dirty furnace filter alarm, something going on with the washer or dryer, tinnitus, your wife is playing a practical joke.