Good idea, thanks! I think they have tried that and didn't get much response. (I'm not sure how many of their neighbors are on it.) I'll see if they're open to trying it again. (Some people are shy and worry about seeming high maintenance, I guess.)

How far off is the alarm? What is the neighborhood comprised of, is it all residental or is there some mixed use? What kind of topography is there- things like tree lined avenues, creeks, fields, buildings, and so on can all create sound corridors or blocks. If it's something that isn't happening regularly, it might only be noticable under certain weather conditions. Like how sound can travel further on fog than when it's clear out.

Could it be that it is an ultra-sonic sound alarm that uses motion sensors to discourage raccoons, skunks, and other critters from doing damage in someone's yard? That would explain why it didn't happen regularly at the same time. A Google search turned up a bunch of them.

-Babka

beesneeds: thanks! It is just residential, on a small hill, and it's generally flat. Since one of the neighbors hears it, I think it is probably not too far away, but, we don't know for sure yet.

Babka NorCal - thanks! That's a good suggestion! I will pass it along. That would definitely explain why it's going off at night.

Thanks, people!

@Babka NorCal 9b: "Could it be that it is an ultra-sonic sound alarm..."

Anything ultrasonic is above 20K and not audible by humans.

Well, it must not be one of those. if people can hear it. Thanks wdccruise.

Wondering if it is coming from inside a house, like alarms that go off if someone falls out of bed or tries to go wandering off during the night (dementia).

Hope the OP will post again when they figure it out.

-Babka

This is a stretch, but are there are any pools around? We occasionally heard what I call a high-pitch whine that sounded like it was coming from the street behind us. Turned out it was coming from our neighbor’s pool equipment. I was going to ask them about it but it stopped a few months ago. It’s either been fixed or has something to do with less use of their pool this time of year. It had to have bothered them, too.

Thanks, everyone!

My friend says it seems to be happening a bit less often now ... which is interesting, although no conclusion can be drawn.

I think I'll try to visit late in the day and see if I can hear it too. (I'm curious now.)

The pool equipment is a good suggestion, although I agree that people with pools can usually hear those alarms (or I guess they wouldn't be very useful), so in theory, if that were the cause then the person would fix it. My friend has a pool so maybe they would know what that was - unless there are a bunch of different kinds now. (I do think there is in general a tend towards making all machines beep ... drives me bananas which is not a long trip ...)

How about a service truck backing up. They always startle me when near my home until I register what it is.

Also, house alarms acccidently set-off. If I forget to turn-off the system and open the wrong door or window the alarm goes-off. I immediately run to turn it off, but I'm sure other folks heard it.

could it be bats? They are active at night and use echolocation to move around, which can at times be heard by some people as high pitched bursts of sound.

Trucks startle me too. I wouldn't think it was a truck late at night though.

I'm sorry about the house alarm going off! That is good to know. I think it was happening too often to be one, but you never know.

Bats! Wow, I never thought of that. I'll suggest it, but I think this was too long of a sound to be a bat. (I've never heard one though.) Very interesting.

Aliens!!👽

“…so in theory, if that were the cause then the person would fix it.”

That’s likely what happened in our case. I got lots of hits when I googled ”pool equipment making high pitched whine.” One link mentioned a failed bearing. It appears to have been fixed.