Someone explained it properly in the reddit thread, it's the exhaust generating noise while driving in reverse (only happens in the morning when cold and at specific RPM, exhaust generates a specific frequency which vibrates the windows and triggers the alarm).
Neighbor's house alarm triggers when I put my car in reverse
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Re: Neighbor's house alarm triggers when I put my car in reverse
#22I don’t know why, but my thought was the same as the third most voted comment in the thread too. The collision avoidance system, which I would have guessed was ultrasound, but the guy on reddit says it’s microwave. Either way, that could be picked up by some kind of sensors in a house alarm system. We live in a crazy world.
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Re: Neighbor's house alarm triggers when I put my car in reverse
#23What I would pay to hear this on Car Talk. Sigh.
Click'n'Clack4eva. You're absolutely right, they'd have had an absolute field day with this.
Re: Neighbor's house alarm triggers when I put my car in reverse
#24Earlier quoted context omitted.
> Is it just me who'd love something like this to happen to me? I love reading about interesting problems and creative ways to solve them. I used to wish for the same. But then I was given a super annoying one. In my apartment I heard this beep about once every 90 seconds or so. I tried ignoring it for a while hoping it'd go away. And just so at the right frequency and infrequent enough Impossible to determine direct…
So what was it?
And what was the app?
Re: Neighbor's house alarm triggers when I put my car in reverse
#25The comment from im_from_detroit [1] seems on-point, possibly ultrasonic sound from a backup sensor on the car being received by an ultrasonic detector in the house. [1] https://www.reddit.com/r/cars/comments/7k12fs/neighbors_hous...
Op mentions later there are no sensors. So either a light/shadow thing or a sound/vibration thing.
Re: Neighbor's house alarm triggers when I put my car in reverse
#26Earlier quoted context omitted.
> Is it just me who'd love something like this to happen to me? I love reading about interesting problems and creative ways to solve them. I used to wish for the same. But then I was given a super annoying one. In my apartment I heard this beep about once every 90 seconds or so. I tried ignoring it for a while hoping it'd go away. And just so at the right frequency and infrequent enough Impossible to determine direct…
So what was it?
Not him but I'd bet 5 bucks it was a smoke alarm with depleted batteries.
Re: Neighbor's house alarm triggers when I put my car in reverse
#27Is it just me who'd love something like this to happen to me? Would be great fun tracking down the source of the problem (if it was my car; probably less so if I was in the house...) There's a lot of options to try to isolate the problem, just thinking out loud here - a) Back into the driveway returning from work. See if alarm goes off. Next morning, see if alarm goes off as you drive out. b) Remove fuse for reverse…
I don't want to be your neighbor :P
Re: Neighbor's house alarm triggers when I put my car in reverse
#28Is it just me who'd love something like this to happen to me? Would be great fun tracking down the source of the problem (if it was my car; probably less so if I was in the house...) There's a lot of options to try to isolate the problem, just thinking out loud here - a) Back into the driveway returning from work. See if alarm goes off. Next morning, see if alarm goes off as you drive out. b) Remove fuse for reverse…
Of what little I read of the reddit thread, there must not be many gear heads in there that debug software, too. I say that only because there is a lot of “it’s probably...”
but no “try this, which will eliminate $FOO. Next, $BAR, which eliminates $FOOBAR.”
For your list, and I’d do a) and not bother with b) and c) as a) eliminates them well enough (point the emitters away from the alarm sensors). For d), I’d put a light cloth in the tailpipe, enough that it will change the exhaust note across RPM range, but the car will still run. Your suggestion leaves the slight possibility of a false positive if we accidentally hit the resonant rpm range. For experimentation only, don’t drive to work a banana in your tailpipe.
One last one: throw it in reverse near the house, but not in your driveway. Could be some weird parabolic blah blah acoustic thing focus thumpy exhaust waves at the house sensors.
I suppose there’s the possibility that a 2.4Ghz radio transmitter of some sort could be responsible, but this way out there and would be way down in my list. SDR and a dongle would be handy here.
Re: Neighbor's house alarm triggers when I put my car in reverse
#29Earlier quoted context omitted.
So what was it?
Not him but I'd bet 5 bucks it was a smoke alarm with depleted batteries.
I'll add a related real life debugging tip I've seen play out at least twice in the real world:
If you can't get an alarm to shut-off or stop beeping, no matter what you try, then give serious thought to the possibility that there's a second alarm nearby which is the source of the noise.
Re: Neighbor's house alarm triggers when I put my car in reverse
#30Is it just me who'd love something like this to happen to me? Would be great fun tracking down the source of the problem (if it was my car; probably less so if I was in the house...) There's a lot of options to try to isolate the problem, just thinking out loud here - a) Back into the driveway returning from work. See if alarm goes off. Next morning, see if alarm goes off as you drive out. b) Remove fuse for reverse…
f) Try putting car in reverse with the engine off [as someone else already said]
I’d be super surprised if that turned up anything. For one thing, okay, we did that and the alarm didn’t go off. What did we eliminate? Alternatively, if the alarm did go off, this ex-mechanic would be at a loss as to how a car with no powered systems could do that. At that point my suggestion is to call a priest.