Can anyone help? I keep hearing a 3 second high pitched beep but can't quite tell where it is coming from n our lounge where our home theatre system is, i.e. LED TV, receiver, speakers, blu ray player, modulator, router, Foxtel box and modem. There are a couple of cable connector boxes behind the system also. I thought it was our fire detectors but I took out the batteries and I could still hear this beep lasting about 3 seconds every 15 minutes. I unplugged the power for the TV and waited 15 minutes - I could still hear the beep. I unplugged the router - still could hear the beep. I unplugged the Foxtel box - still could hear the beep. I unplugged the receiver - still heard this annoying beep. Any ideas? Thanks John in Canberra, Australia

  • 4
    Are your smoke alarms hard wired? If so, they may be beeping because the batteries are out of them. Other source of beeping (at least for me) are my uninterruptable power supplies. If you have any of those, I'd check them too.
    – Comintern
    Apr 13, 2015 at 5:04
  • Another possibility is a dead/dying battery backup for an alarm system. But you see the theme -- it's most likely a dead battery in something. Apr 13, 2015 at 13:54
  • Do you have a Carbon Monoxide detector anywhere? This is likely near the floor, not on the ceiling. Apr 13, 2015 at 18:40
  • This sounds like one of those hidden beeper pranks to me. youtube.com/watch?v=NU6cSI0GQOY Apr 13, 2015 at 21:00
  • In addition to the duplicate this is linked to, there are other duplicate questions here, here, and here
    – BMitch
    Apr 15, 2015 at 19:21

2 Answers 2


The only thing I have ever heard of making the high pitched beep at intervals is fire or house alarms. If you have a dead battery in your fire alarm it will go straight to its backup power and beep. Given the pitch and the proximity to the ceiling and how well the sound echoes it can drive you nuts.

The thing is most of the time these alarms are all installed at the same time. So if you try to figure out which one it is and which battery to replace, well you are doing the same thing a week from now. And we all know that batteries only die between 1-6 AM.


Some carbon monoxide detectors have a warning beep when the unit reaches it's end-of-life point. This is because of the limited lifetime of the detector, and is independent of any low-battery warning. It cannot be switched off; you need to replace the unit...

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