On Sat, 3 Oct 2009 11:27:35 -0400, "Robert Green"
wrote:

I was at an elderly friend's house the other day when the smoke alarm went
off. It was quite loud and I reacted instantly to the noise. My friend, a
former Army marksman in his 70's, who's suffering from profound high
frequency hearing loss, heard nothing!!!

Then I started looking around for alarms that used lower frequency sounders
but the only thing I could find were specially converted smoke detectors
that cost $300!!!!

I'm wondering why COTS alarms operate at such a high sound frequency,

They do? I have an AC smoke alarm and I've had a couple battery ones,
and they seem to be mid-range. (I've played the piano for 50 years,
but still have little idea what note they are, or even what octave,
but they still seem midrange. I'll guess, middle C. The nearby A is
440, so C must be 500 to 550 cps.)

It sounds like a metallic kazoo, or a trombone at its mid-pitch.

especially when it's well known that older adults lose their high frequency
hearing first. I have been thinking of just unsoldering the Sonalert
sounders in low priced alarms and replacing them with lower frequency

Have they switched to little, high frequency sonalerts. They used to
use ones as big as demitasse coffe cup. Bigger than that. More like a
tea cup at a Chinese restaurant. They don't use that anymore? The
bigger they are, the lower the pitch, right?

I would say to look for old ones, but one of the two styles of smoke
detector doesn't work well after it is old, they say. Doesn't the
other kind still work well when it is old? Which is which?

sounders, but that could compromise the detector's ability to sense smoke if
the replacement sounder has sufficiently different electrical
characteristics.

If you look at mouser.com I believe they sell a wide range of
sonalerts and may give frequencies and probalby give specs. Best to
use a high-speed connection becauase last I looked two years ago,
every search dl's a pdf rep of the page in the catalog. So it takes a
few seconds even with lo-speed dsl. But if they sell something, it
seems they have every model of it, by more than one maker.

Well, they don't seem to use pdf anymore, and it loads much quicker
http://www.mouser.com/Search/Refine....yword=sonalert but there
don't seem to be pictures on this page, plus you will have to click on
data sheet for specs.

Does anyone know of a *reasonably* priced smoke detector whose sounder is
audible to people with high frequency hearing loss? I'd like to buy a
couple of such detectors for him, but the price on the only unit I've found
would bring the bill to over $1200 for four detectors, and that's just
unreasonable. I know what goes into making a smoke detector and 10x the
cost of the parts still wouldn't bring the price that high.

P&M, because you're being nice to an old person.