We have a sound similar to a smoke detector when it needs a battery change but it isn’t the smoke detectors (we have removed the batteries and disabled them right now) nor the CO detectors. It is sometimes a small chirp and other times louder. It happens every 30 seconds day and night. It isn’t an animal. It sounds like it is coming from the kitchen or that general area but it seems to move a little bit and not from one specific area. Anyone have any ideas?

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    Would unplug or turn off breaker(stoves) each appliance one at a time, include clocks, thermostats, lights(?). Sound might travel though vents/ductwork in the walls. Makes it easier since sound is constant, not random.
    – crip659
    Commented Nov 22, 2021 at 15:31
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    @manassehkatz-Moving2Codidact Gonna pick up a dozen of those.. lol
    – JACK
    Commented Nov 22, 2021 at 16:30
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    When disabling smoke detectors did you disconnect them from AC power? If not, they will continue to chirp until you replace the battery with a fresh one.
    – HoneyDo
    Commented Nov 22, 2021 at 16:40
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    That's almost certainly got to be a smoke detector, which beep every 30 to indicate low battery; maybe one in the attic? In term of varying loudness, that can be thermal effects on the battery - when warmer it can release more energy and is thus louder, whereas at night it's colder and quieter. That also suggests temp swings which points to an attic.
    – dandavis
    Commented Nov 22, 2021 at 17:57

1 Answer 1


Expanding on my comment, I suggest a couple of binary searches. That basically means splitting the house into two zones, and working out which zone the beeping is in, then splitting that into two subzones.

These are best done when you're alone in the house. You might get lucky and end up sitting right near the source.

The first is to work out whether it's louder at the top or the bottom of the stairs. Sound travels in funny ways especially if you have air ducting, but that should narrow it down to a particular floor.

Say it's upstairs: open half the doors onto the landing and close the others. When you have a feel for the volume, swap the open/closed doors. Louder or quieter? Don't forget hatches/doors into attics and basements, even storage closets - alarm units can be placed in strange places.

Easier with an assistant is turn off the power to the house: does it stop the noise? I'd wait a couple of minutes as a few things hold enough charge to be annoying for a short period. If not, it's got to be something with a battery of some form. But if killing power does stop the problem, back to the binary search: turn only half the circuits back on. If the noise comes back, the problem device is in one of those; if not, it's in the other half. Divide the noisy half in two again and continue.

Once you're down to one circuit, turn off all the others, and start unplugging everything on the noisy circuit. Don't just press the off switch on devices, plug the plug out of the wall (even if it looks like a real mains switch, it still might not be in some cases).

My suspicion would still lie with anything that is known to be able to beep:

  • Starting with smoke alarms that are likely to beep if they have mains, battery, or both. 30s is a plausible period for them.
  • It's also plausible for microwaves: I've had one that beeped every minute after finishing, until the door was opened, but on one in work it's 30s.
  • I've also had issues with a burglar alarm main unit built into my airing cupboard. The lead-acid backup battery doesn't like being kept so warm, and the first I knew it had failed was when it made an intermittent noise after we'd had a power cut.

If you've got kids, try to get them involved - sensitivity to high pitches reduces with age, so they may be able to hear it more clearly than you, and a small prize for the one who finds the culprit is a great incentive. Their help would of course need to be age-appropriate, but even quite young ones can call out the effects when you flip breakers.

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