njd-srien is a siren built with VueJS and based on the WebAudioAPI, it is famous in reggae and sound-system culture.
The principle is a a main oscillator that produces a wave. Beside, another oscillator that we call the low frequency oscillator (LFO) produces another wave. The oscillations of the LFO are modifying the frequency of the main oscillator, as a result, the amplitude of the main oscillations are changing, this is called modulation. The result is a siren that sounds like the cops, of the ambulance.
The siren is hosted here.
You can play with multiple parameters :
- Speed
- Tone
- Wave form
- Volume
There is also a delay, based on Tuna.