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

[studio460]

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!

[BlinkyLights]

Look up "dub sirens" for a similar thing.

[dubonaire]

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.

[studio460]

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.

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.

[jamos]

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

[Dave Peck]

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.

[studio460]

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).

[studio460]

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!

[Dave Peck]

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.