FIREWORKS!

Being the pyro that I am I love the 4th of july and fireworks. I've always wondered how some fireworks make that loud whistling sound as they ascend. This is the answer I found on this website which interviews a pyrotechnician who makes fireworks.

-What happens with the whistler rocket is that you have your rocket whistler composition, and it's in a cardboard tube that's only filled a quarter of the way at the top end of the tube. The rest of the tube is open. When you ignite your whistler from the open ended cardboard tube, as it burns, you get small sparks and explosions occurring. These small explosions cause the cardboard tube to vibrate. As it's vibrating, just like a tuning fork, you actually get a resonant sound occurring

well there you go. Have a happy 4th of july