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 ) -- Ferkelparadeπ 22:14, 17 Jan 2005 (UTC)
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)
