How is a smoke detector so loud?
April 26, 2004 2:48 PM   Subscribe

What is the component in a smoke detector/fire alarm that can produce such a high volume noise from a 9v battery? (more inside)

I am intrigued by the sheer volume a smoke alarm can put out. As a cycle commuter, I'm thinking about constructing some kind of horn, and am wondering if I could cook something up from a dismembered smoke alarm.
posted by i_am_joe's_spleen to Technology (8 answers total)
It's a piezo element. Given those words you should be able to find out anything you want to know.
posted by xil at 2:50 PM on April 26, 2004

If the buzzer is surface mount it might be easier to just go to radio shack and pick up another. They have all types. They are a bit expensive there though (about $5 for a real loud one).
posted by estey at 2:59 PM on April 26, 2004

Note that you'll find that what is loud in the context of indoors is surprisingly much less so out-of-doors.
posted by Ethereal Bligh at 3:11 PM on April 26, 2004

Consider the possibility of modifying your home grown horn so that it varies in volume and/or pitch. Humans are much more sensitive to changes in the auditory landscape than the landscape itself, just like the dinosaurs in Jurassic Park. :)
posted by yangwar at 3:42 PM on April 26, 2004

Not forgetting the radioactive side of things...
posted by dash_slot- at 4:54 PM on April 26, 2004

What you want is a piezoelectric transducer (basically a piezo element and driver circuitry).

If you look around, you can probably find a cheap "panic button" or "personal alarm" type device that includes everything you need for under $10.
posted by mmoncur at 1:19 AM on April 27, 2004

You know what? You're going to make a wicked loud noise like a smoke alarm and no one is going think that it's coming from you. We're trained that way. In traffic, the noise we pay attention to is the car horn, so if you're in MacGuyver mode, rig up something that sounds like a car horn (air horn, maybe?). And this is not a place I would pinch pennies...your safety is too important. Good luck!
posted by stupidsexyFlanders at 8:17 AM on April 27, 2004

Thanks everyone.

Yeah, ssF, I know. I was hoping that the available pitch range would be a bit bigger than the piezo devices seem to have, but I still have some research to do now that I've had these pointers.

And don't think I haven't pondered how to build up a reservoir of compressed air to power a horn...
posted by i_am_joe's_spleen at 2:21 PM on April 27, 2004

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