How do I make an air-raid siren? [Eurorack]

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studio460
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How do I make an air-raid siren? [Eurorack]

Post by studio460 » Wed Jan 13, 2021 8:55 pm

I really love this sound (maybe there should be a "sound effects" sub-forum?). They used to run air-raid drills in Los Angeles ages ago and there's still a couple of air-raid towers in mid-city. But how would you go about crafting one in modular? I've got a single Braids' sawtooth with a slow LFO modulating the pitch up and down. Should I try using two waves slightly de-tuned? The "up" sounds okay, but there's something "off" with the "down." Almost like a Doppler-effect or something, or a slight de-tune as the real one oscillates lower. The general vibe is there, but when pitch lowers on the real one, some other stuff seems to be happening sonicially. A quick Google-search showed a couple of DIY siren-builds like this one:https://www.instructables.com/DIY-Air-Raid-Siren/

I think the air-fluttery sound is illustrated in the DIY-build. Also, police sirens have a certain growl in the mid- and lower-frequencies. Not sure how to mimic that accurately. So I would also like to be able craft a decent Wheelen police-siren somehow.

So in the air-raid siren, you've got the pitch slowly going up and down, something adding that "flutter" or "growl," and I suppose some reverb for that "Godzilla" effect. Also, the specific pitch-range seems to be important in capturing the correct sound—I need to figure out how many steps or half-steps (or less) are in the interval the real ones use. Any tips appreciated!
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Re: How do I make an air-raid siren? [Eurorack]

Post by BlinkyLights » Wed Jan 13, 2021 9:05 pm

Look up "dub sirens" for a similar thing.

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Re: How do I make an air-raid siren? [Eurorack]

Post by dubonaire » Wed Jan 13, 2021 9:14 pm

The amplitude changes along with the pitch because the rotor motor speeds up and slows down. So you would need the CV to adjust Osc pitch in a 100Hz range somewhere between 400-600 Hz roughly and also a VCA. Maybe try mixing a sine and pulse.

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Re: How do I make an air-raid siren? [Eurorack]

Post by studio460 » Wed Jan 13, 2021 10:20 pm

BlinkyLights wrote:
Wed Jan 13, 2021 9:05 pm
Look up "dub sirens" for a similar thing.
Wow! Cool! Oh. I thought they were like real sirens. But thanks anyway; maybe I can learn few tricks from those.
dubonaire wrote:
Wed Jan 13, 2021 9:14 pm
The amplitude changes along with the pitch because the rotor motor speeds up and slows down. So you would need the CV to adjust Osc pitch in a 100Hz range somewhere between 400-600 Hz roughly and also a VCA. Maybe try mixing a sine and pulse.
Got it! Right, the rotor speed changes, so I need to vary amplitude, too. Excellent tips! I'll try those out! Thanks! Anyone else? This is seemingly trickier to do that I had initially thought. I think the pitch-range in particular may be key.
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Re: How do I make an air-raid siren? [Eurorack]

Post by jamos » Wed Jan 13, 2021 10:34 pm

I have a patch I did on my Nord modular... I wrote out the theory I think. Let me find a link...

https://electro-music.com/forum/viewtop ... en&t=36903

Oops no writeup, and the theory page I linked to is kaput. If you download the patch file you can view it in the online G2 patch viewer...

https://electro-music.com/patchviewer/? ... p?id=15260
Nord Modular G2 & G2X, Emulator X, MPC Live, and a growing Euro system.

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Re: How do I make an air-raid siren? [Eurorack]

Post by Dave Peck » Thu Jan 14, 2021 12:42 am

An air raid siren produced two pitches, tuned a major third apart. For example tune one saw osc to "C" and tune another to "E".

Patch them both through a lowpass filter and roll off the high end.

Add slow up/down pitch bend, either manually or with a slow LFO applied to both oscs.

Crank up the reverb, and roll the high end off of the reverb.

Viola.

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Re: How do I make an air-raid siren? [Eurorack]

Post by studio460 » Thu Jan 14, 2021 9:24 pm

jamos wrote:
Wed Jan 13, 2021 10:34 pm
I have a patch I did on my Nord modular . . .
Thanks, but I can't open a pch2 file? Oh, I got it (looked at the second link).
Last edited by studio460 on Thu Jan 14, 2021 9:28 pm, edited 1 time in total.
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Re: How do I make an air-raid siren? [Eurorack]

Post by studio460 » Thu Jan 14, 2021 9:25 pm

Dave Peck wrote:
Thu Jan 14, 2021 12:42 am
An air raid siren produced two pitches, tuned a major third apart. For example tune one saw osc to "C" and tune another to "E".

Patch them both through a lowpass filter and roll off the high end.

Add slow up/down pitch bend, either manually or with a slow LFO applied to both oscs.

Crank up the reverb, and roll the high end off of the reverb.

Viola.
Holy sh*t! That is so cool! Did you just figure that out by ear? Thank you very much for the step-by-step instructions—so helpful!!! I knew there was more to it. Can't wait to try that out!
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Re: How do I make an air-raid siren? [Eurorack]

Post by Dave Peck » Thu Jan 14, 2021 10:52 pm

studio460 wrote:
Thu Jan 14, 2021 9:25 pm

Holy sh*t! That is so cool! Did you just figure that out by ear? Thank you very much for the step-by-step instructions—so helpful!!! I knew there was more to it. Can't wait to try that out!
Yep, figured it out by listening, and then replicated it. First time I made a patch for this effect was many many years ago when I was playing synths in a progressive metal band in L.A. and we blatantly stole the idea from the intro of Black Sabbath's "War Pigs". Years later I also used it in a Nord Modular patch I created called "Autodestruct.pch" that combines this effect plus a couple of classic sci-fi 'alarm' sound effects plus random massive explosions, replicating the spaceship's auto destruct countdown scene from about a hundred 80's sci-fi action flicks.

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