How to detect (non-smart) smoke alarm sounds? (DIY Alexa Guard)

is there a good way to detect smoke alarm sounds so that the alarms can be made available in Home Assistant?

I’m aware that there are Zwave smoke detectors and other RF-based ones that may be directly integrable, but they are all pretty expensive for what they are and - apparently at least for the zwave ones - rather unreliable because of frequent false positives. I do not want to spend 50€ for something that goes off in the middle of the night for no reason AND that has to be replaced every couple years.

So, ideally I would like to equip my rooms with regular, dumb, non-connected smoke alarms and just detect the alarm sound.

I’m aware that this would not be 100% reliable in all situations, but for certain house layouts with rather short distances this should theoretically be possible.
The frequency, duration and - depending on the location - also the volume of the alarms should be detectable.
I think certain cameras are able to do this (Wyze?) and every “smart” speakers could easily do this if they wanted to.

So has anyone done that?
What would be the best way(s) to achieve this?

If there was alarm detection like this it could probably also be trained to detect other alarms (e.g. car alarms, water leak, open fridge door, etc.).


EDIT: Amazon has announced such a feature for the Echos. It’s called “Alexa guard”.

Rather than trying to detect the sound why not use a regular detector with alarm output and hook it up to an ESP or Pi:

Well, if you only have 1 detector this might be an approach, but for 3-4 it is not really practicable as all of them would need to be hooked up to an ESP or be interconnected .

I have four of them. They all have 12V power cabling in the roof back to a central power supply. They have alarm cabling back to a central point to. I was going to wire them to the PI running HA but GPIO inputs are a poorly implemented component so I am now going to put a $7 WEMOS D1 ESP module at each location and use the alarm cabling to send 5V to power them.

However I understand that not everyone can (or wants to) crawl around in the roof space.

Ok, in your situation this is possible because you have easy access to the wiring…

Well it wasn’t easy. A day of sweaty and itchy work in the roof.

Did you see this?

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