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Old 18th March 2008, 05:27 AM   #1
TheMG is offline TheMG  Canada
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Default air raid siren

I just got this crazy idea...

Everyone knows the characteristic sound of a two-tone air raid siren right? For those who don't know what I'm talking about: http://youtube.com/watch?v=S3Z91xfFZ1U

Ok, so here's the idea: building some type of circuit to emulate that sound.

From my research so far I've found out the two tones are at a 5/6 pitch ratio, and go up to about 500Hz on full speed.

So the circuit would have to produce these two tones, maintaining the same ratio all the while the frequency and amplitude goes down and back up according to what I think would be a triangle wave (simulating the spinning up and down of the motor).

I don't know yet, but I think a little distortion would be welcomed for a more "realistic" sound.

If I/we succeed, that should make for a kick*** alarm clock, doorbell, whatever other use you might think of!

Ok go!
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Old 23rd March 2008, 12:46 AM   #2
eStatic is offline eStatic  United States
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Default Re: air raid siren

Quote:
Originally posted by TheMG
If I/we succeed, that should make for a kick*** alarm clock, doorbell, whatever other use you might think of!
Ok go!
Right! A sound to remind you that your fellow man is likely to blow you and your loved ones to burning hell. I love it. Maybe you could have screams of agony from women and children segued in after the siren dies down. That would really be kick*** eh?

Donít' mind me, I've just got this problem where I have an immediate puke response to the smell of burning flesh.
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Old 23rd March 2008, 07:56 PM   #3
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A 555 timer chip would be a good place to start.Two of them tuned to a 5/6 ratio,and another one used to vary the freq.Not sure how well they would track,but might make interesting sound as they go in and out of tune,especially at 110-120 db. :-)

Another way would be to make a master osc,and divide the output by 10 and 12 to get the two tones.If you want to get fancy,you could add an additional LFO (1/20 hz) to simulate the doppler shift of a rotating siren.

If you are not already familiar with it,do a Google search for the Big Red Chrysler air raid siren.(victorysiren.com)Also search 555 timer,and siren circuits.
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Old 24th March 2008, 10:06 PM   #4
Pano is offline Pano  United States
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Not something I would want to do.

We have Tsunami warning sirens here in Hawaii. Similar sound.

They test them the first weekday of every month.
So your circuit would have me running for high ground, or running to take my landlord the rent check!
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Old 29th March 2008, 01:34 AM   #5
TheMG is offline TheMG  Canada
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Lol, I don't know, but for some reason I like the sound. Again, don't ask me why.

Fact: I've never heard such a siren in real life, and to the best of my knowledge there are no such sirens installed/used over here.

I don't know if I'll ever actually attempt this project now that I think about it. Haven't got the time currently. Don't even ask where the idea came from.
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Old 29th March 2008, 09:57 PM   #6
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You need to experience one of these in "person" to get the full effect,not only are they insanely loud,they vibrate your entire body.

As "cool" as they may be,(along with truck,train,and boat horns,steam whistles,etc)they are not toys,and besides the serious hearing damage potential,your neighbors and the local law will not be amused,since they warn of impending disaster.

Anyway,an electronic version that can be kept to a reasonable volume seems to be a sensible project.

Or you can get an aoogha horn on Ebay for about $40.00

Let's see you sleep through that!
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Old 30th March 2008, 12:23 AM   #7
TheMG is offline TheMG  Canada
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Yeah, that was part of the electronic idea. Very difficult to make a small scale (read: much less loud) siren such as this while staying true to the sound of the real thing. An electronic version, assuming the sound produced can be made to resemble the real thing, can be adjusted as loud or as silent as needed.
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Old 30th March 2008, 11:25 AM   #8
OzMikeH is offline OzMikeH  Australia
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On occasion I need to work on equipment in close proximity to those sirens which may go off ay any time. The spec sheet says they produce 153 dB. I have no idea what the distance that level is measured at.
When we go near them if they are not isolated we have to wear ear plugs and ear muffs. They will not protect my hearing, but they will reduce the level enough so you can run away from the siren before going deaf. You have to stick your fingers in your ears 200m away.
I've never experienced one going off, I imagine it would shake the snot out of your nose.

I suggest you get a sound recorder/player chip. I used to use them for automated voice prompts for radio controlled runway lighting. Very easy to use.

I think your doorbell should play the sound of someone knocking on the door....
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Old 31st March 2008, 04:41 AM   #9
Pano is offline Pano  United States
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Quote:
Originally posted by OzMikeH
I think your doorbell should play the sound of someone knocking on the door....
He-he... My mobile phone rings like a good old telephone bell. That's the retro spirit! (I like the knocking doorbell even better)
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Old 2nd April 2008, 01:28 AM   #10
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i once made the sound on an EMC (analog) synthesizer in high school. i used square waves and two VCO's running off of a common control voltage and added a bit of tape echo with a 500mS delay to get it to sound just right. the sound should maintain the 5/6 ratio, as the real siren uses a spinning cylinder with two separate sets of slots in it (the slots are the reason i chose square waves, and the sets of slots are on the same cylinder,and that's the reason for maintaining the ratio). you may want to simulate the spinup and spindown sequences as well. since (at least here in Colorado) the horns on these sirens rotate, you may want to add a 20% depth tremolo with a rate of about 0.3hz. in other parts of the country, such as Massachusetts the slow tremolo doesn't exist, since the raw siren is mounted on telephone poles
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