User:Ryguasu/Sirens

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[edit] Digitally Synthesizing Siren Sounds (Police, Air-raid, etc.)

I'm trying to write a program to produce various types of siren sounds, so as to immitate police sirens, abulance sirens, air-raid sirens, etc.. I already have a program that can take a sine wave and modulate the pitch up and down to create a bad impression of a siren. Unfortunately, the result sounds more like someone playing with the pitch-bend wheel on an analog synth than any siren one might actually hear in the real world. I suspect I'd get pretty similar results if I substituted, say, a square wave or a triangle wave for the sine wave in my program.

Does anyone know if there are any easy-to-synthesize waveforms that might sound more like a siren? Or am I going to need to actually go out and digitize sounds from a real-life siren (a la Sampler (musical instrument))? --Ryguasu 04:58, 17 Jan 2005 (UTC)

  • A simple sine wave might be a good starting point for a siren sound, but sounds in the real world are generally made up of a number of different waveforms at different frequencies - for a halfway believable siren, you might try adding some harmonic overtones and maybe a tiny bit of phase distortion (more of both for a classic air raid siren than for a modern police siren). It also seems that with most sirens, different frequencies aren't shifted up and down by the same pitch which leads to a slightly more distorted sound as the siren's wail reaches its highest pitch - I guess it would be pretty tricky to sysntheize a naturally-sounding siren unless you either have a pretty detailed idea what you are doing or you are willing to experiment for a couple of hours with some wave-shaping software (which is generally great fun but rarely leads to the results you were trying to achieve - at least, that's the case with most of my synth experiments :P ) -- Ferkelparade π 22:14, 17 Jan 2005 (UTC)
    • Here's a spectrogram of a london-style police siren
      Here's a spectrogram of a london-style police siren
      . As Ferkelparade said, you'd need multiple frequency sources to get the overtones. Notice that the highest frequencies bend up over a longer time period than the root frequency. Also note that this siren has 2 separate whistles, overlapping in time. An alternative to multiple sines or sampling the whole siren would be to record a siren, then take a small looped sample while it is steady at its highest frequency. Then you could pitch bend one or more copies of that waveform to get different siren patterns. -Key45 22:57, 17 Jan 2005 (UTC)
      • Speaking of synthesizing instrument sounds, I've been trying to make them using overlapped sine waves at different frequencies and amplitudes, but it doesn't seem to work. What am I doing wrong, and where can I find analyses of real instruments to work from? Alphax (t) (c) (e) 16:27, Jan 18, 2005 (UTC)