Last night, right after I went to bed, I heard some quietish beeping, seven or eight beeps, that I’ve never heard before. It happened too fast to get a bead on where it was coming from. It sort of sounded like an alarm from a watch but I don’t have a watch. I lay there waiting for it to happen again but it didn’t. So, of course, I couldn’t sleep and started wondering what caused it. All the electronics in the house are at least three years old and I know all the sounds they make. I couldn’t come up with anything that might be the culprit. Eventually, I got up and walked through the house. Nothing was amiss, no blinking lights. I went through the house again today but can’t find anything that might have caused this and it hasn’t happened again. I HATE it when these kind of weird things happen! It will vex me for days.
Last time this happened to me it turned out that I left a refrigerator door slightly open.
And when it happened to me, it was the smoke detector warning of a dying battery. What confused me was that this occurred on the Saturday of Daylight Saving Time change. There’s a public service message suggesting that occasion is a convenient one to replace the smoke detector batteries, so I was amazed that the detector apparently knew the date to prompt me. (In reality, just a coincidence.)
Try not to stress about it; it may never happen again, and if it does, you’ll be prepared.
My smoke detectors make one loud beep every few minutes when they need batteries. Almost always happens in the middle of the night just to wake me in a panic. These beeps happened over several seconds.
Good advice but my mind won’t listen. Those beeps came from somewhere and it takes time for me to accept “unexplained”.
It’s sometimes a great advantage to have hearing loss and tinnitus. I can rarely hear those faint random beeps over the noise in my head. Drove me nuts decades ago. But not now.
So you have that to look forward to. 
I’m thinking intruder(I’m looking at you Little greys).
Yep. Aliens.
Time to move 
I have a sweater shaver that did this to me til I happened to be holding it my hand, and it beeped. I looked for weeks. It needed put on its charger.
Anything rechargeable might do this.
Flashlights. Shavers. Little desktop conviences. Any number of things. Make sure you looked at everything.
Good luck. Tell us if you find it.
This happens to me way more often than I care to admit and I meticulously try to examine and locate the origin of the mysterious sounds. If I don’t my mind creates all kinds of potential catastrophes.
On one occasion many years ago the annoying sound turned out to be an old 1990s Christmas card with animated music stashed in my basement. It just wouldn’t die.
It started bleeping an anemic version of Jungle Bells that you could only hear at certain spots in the house. I thought I was going mad and tore the house apart in my quest for silence.
I have recently taken to wearing earplugs in my house just so I don’t have to hear most of this stuff.
If I do hear something it is generally pretty loud and I should probably pay attention.
Now that’s a cover I’d like to hear!
I was thinking someone standing outside my window wearing a watch that had an alarm set for 3:30 a.m. 
I don’t have anything rechargeable. But it must be something small hidden away somewhere. I did track down a sound once that came from old batteries in a tabletop water fountain that was up on a high shelf. But it was buzzing.
That’s almost exactly what I wanted to post after reading it 
. Must have a lot of drums instead of jingles.
Dashing ‘cross the veldt
In a one buff’ open sleigh
o’er the grass we go
laughing all the way
…
When I had to replace my wired smoke+CO detectors recently, I specifically ordered the “no-batteries” model. I figured the chances of having a fire and a power failure at the same time were not worth the guarantee of having the things howl at me to replace the batteries. FWIW, I also have a plug-in CO monitor that does have battery backup. At least I don’t have to climb a ladder to the ceiling to replace the battery!
I’m quite bothered by mysterious beeps but it usually turns out to be something outside.
PSA: If you have combined smoke and CO alarms, be aware of the different sounds. On mine, a smoke alarm is a constant series of deafeningly loud beeps; a CO alarm is a cycle of four beeps, pause, and four beeps. There will also be a quiet beep every few minutes or so indicating the need to replace the smoke/CO detector.
I got a new smart window air conditioner last summer. It’s one of those U-shaped models that allows a sash window to be nearly closed down the middle, isolating the motor and compressor outside, behind the glass for quiet performance. As such, it is permanently mounted, year round.
So this winter has been a cold one, with several cold snaps below zero. Every time it drops belore zero, I hear a soft, intermittent beep. Took a while to track it down. Not sure why it’s beeping, we’ll find out when I turn it on next summer.
Oh my that’s a dramatic typo lol!
The first thing I checked was the CO alarm because I’m not sure what noise it makes. But I really knew it wasn’t that because these were not OMG EMERGENCY! beeps. They were quietish and if I had been asleep, I doubt I would have heard them.
I recently had some mysterious beeps, which would happen every few minutes. I first assumed it was a smoke detector, but standing near each smoke detector in turn didn’t reveal a culprit. Eventually, after several hours of sleuthing, it turned out to be my printer asking for permission to upgrade its firmware.
Look, Mr. Printer, your firmware is not that important. Just silently upgrade it if you want to. Or display a message and wait until I get around to noticing it. Or send the message to my PC. You’re not important enough to interrupt my day with beeps.
Any medical or personal care items in your house.
You’ve narrowed down the search area by the loudness of the beeps. Do a test with things you know you have that beep. Place them in different locations in your house and see how loud it needs to be for you to hear it from your bedroom. Just an idea.
You must understand this from the perspective of the printer developers. This is their mission, their livelihood – this what they live for! Keeping your printer firmware up to date is their career. So of course it’s at least as important as a fire warning. If they had their prefernces, if you didn’t upgrade the firmware by a certain time the printer would either stop working or, preferably, catch on fire to teach you a lesson!