Why fireworks whistle

[pussing]

Why do fireworks whistle? Do they whistle anyway, or is something put in them to make them whistle?

[incitatus]

Its the way the opening is designed. If you push a large volume of gas through a small hole it will whistle. The firework designers arrange a small hole for the hot gases to escape through. It's the same principle as the whistling kettle.

[Peter R]

Incitatus is perfectly right, but there's a lot more to it. The reason that the hole (nozzle) makes noise is because the fuel does not burn perfectly - just like an imperfect car engine makes noise, or, yes, a kettle. The rate at which the fuel burns, or water boils, fluctuates (wobbles) Also, some propellants, such as those for fireworks, are specially designed to make noise as they burn by being specially unstable! If you ever see military rocket launches, there can be a similar noise made by the vibration of the fins, but only at very high velocities