Designing an Old School Air Raid or Police Siren in FM8

One of the really great things about working with FM8 is learning how many of the familiar sounds in our modern world can be made through frequency modulation synthesis. This tutorial shows you how to recreate an air raid siren, which can be used in music, sound design for movies and just for fun.

Whether you are recreating classic telephone signals or classical orchestral strings, FM8 is a streamlined approach for FM synthesis and it makes producing sounds like the one we will make today very easy. And honestly, there is usually more than one way to create many of these familiar sounds, so I always recommend you experiment and try to come up with other ways to arrive at the same sound on your own.

To get this sound started you first need to route the F Operator to the output and pan it all the way to the right. Now route Operator E to the output and pan it all the way to the left. A Soft Tristate waveform is loaded into Operator F, which is also fed back into itself between 20% and 25%. A Short Tristate waveform is loaded into Operator E, which is also fed back into itself the same amount. Now Operator D is set up with the default Sine waveform and set to modulate both Operators E and F. It is also fed back into itself. This gives us our core sound.

Next, all three oscillator’s envelopes are linked together and set up the same way to ensure consistent delivery and development of sound. We want this to sound like one noise, not layered.

Now, we add a total of five effects. The Overdrive, Tube Amp and Cabinet all work together to give us the old-time, almost distant character that all air raid sirens seem to have, plus that bit of grit starts to enter into the sound at this point. It may not seem like much, but it is these small artifacts that help the sounds to cut through other noise and carry. Now the Tremolo and Reverb give the sound a small amount of movement and the space needed to develop in.

The last stop is the Master window. Here we need to increase both the Polyphony and Unison Voices above thirty to get the right push in the sound, after all this is a siren. Now turn the Digital Quality slider all the way up, set it to operate in Mono mode, turn on the Portamento and adjust the Time slider until the glide is just right. That’s it!

Below you can hear an audio sample of this sound in action. You can also achieve similar results modulating the pitch through an LFO or envelope. I chose to use a glide because it gives more control over timing, which makes it easier to sync it with film scenes. It also provides a more real hand-cranked feel, so it comes across as more authentic and old-school. It can also easily be used as an old police siren.

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Cheers,
OhmLab