Definition
A whistle is a tube whose composition, based on potassium benzoate or salicylate, burns in rapid pulses that set the air column of the tube resonating and produce a shrill whistle, rising or falling depending on the geometry. It is almost always paired with propulsion: candle or cake whistles screaming up to 20-40 m, mine whistles thrown in a spray, or whistling bombettes released by a 75 to 125 mm shell. A whistle cake, 25 to 100 shots over 20 to 40 seconds, makes an easily placed sonic highlight. The effect can be combined with a silver trail or a crackling tip. Like the salute, the whistle is a noise effect to be dosed carefully on sites close to housing.
In practice, for the display company
A whistle cake costs one cue yet is heard a kilometre away: it is the effect you pull from a late wedding show and keep for the town festival. PyroDesk tags the sound effect on the product sheet, and PyroSimulator plays the whistle synchronised with the trajectory, which helps balance the soundtrack of a pyromusical.