system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:What makes that 'pewww' sound, as fireworks get shot into the air?
gpt
As far as i know it is a pyrotechnic mixture called whistle mix. The two main components are potassium perchlorate and sodium salicylate or sodium benzoate. The powdered mix is pressed into a tube carefully (as it is sensitive to impact and friction) and when ignited acts like a rocket propellant which creates a high pitch whistling noise as the gases escape from the bottom. Titanium powder can be added for white sparks and iron oxide can be added to catalyse the reaction. The size and shape of the tube can change the sound of the whistle.