Love them or loath them but fireworks can be full of noise. You have big bangs, whizzing whistles and thunderous thud sounds to fill up the night sky. For some these different noises are the best part of fireworks, while others aren’t as excited about them.
We’ve previously looked at how fireworks get their colours and decided to venture into the wonderful world of sound next. The science behind the different sound effects is not as simple as it seems!
Just about the Explosive Gunpowder?
It’s easy to assume that the explosion of the gunpowder is behind the sound and that’s it. But it isn’t quite as simple as that since different sound effects require a bit more chemistry.
Furthermore, the explosion of the firework isn’t the only occasion for the sound to make presence. For example, when you shoot certain types of fireworks, such as rockets, you’ll hear the whistling sound as the firework goes up and then a bang as it explodes.
Just like firework manufacturers did with the colours, they found out that different chemicals create different sounds. By controlling the way the chemicals heat up and the way they are released, they were able to create a number of unique sound effects.
Creating Different Sound Effects
By controlling the shape of the firework cartridge and the chemicals inside these tubes, you’ll get to enjoy the different unique sounds. This is because different chemicals have different reaction times. The reaction times to the chemicals being burned can either be fast or slow.
Slow reacting chemicals are behind the vibrating sound effects. So, whistles and warbling sounds are due to the chemicals reacting slower to the heat. On the other hand, fast reacting chemicals instantly go from a solid to a gas, creating an explosive effect. This in turn, creates a shock wave of sound and causes the bangs, and the thuds.
Here’s a more detailed look of the most commonly used sound effects:
- Loud bangs – the most common is naturally the bang. This is created by confining the explosion inside a small shell. The gases expand much quicker than the speed of sound and therefore, the cartridge explodes it creates a loud, sonic boom.
- Crackling noise – the crackling sound is mainly to do with chemistry. The fireworks are filled with lead oxide, which turns into lead atoms as the firework explodes and heat up. These lead atoms vaporize in the huge heat and the vapours make the crackling sound as they expand.
- Whistling sounds – the whistle is down to the tube being a narrow one, thus rockets often make a whistling noise. The narrow tube ensures the mixture of chemicals doesn’t burn too quick and that it won’t explode until later on in the air. Half of the narrow tube remains empty and once the firework is lit up, the empty part of the tube will vibrate and make the whistling sound.
Interestingly enough, fireworks were mainly used at the start for the funky sound effects. The crackling, popping sounds of the first firecrackers were thought to be helpful in warding off evil spirits and ghosts.
For many, the love of fireworks remains strong because of the exhilarating sound effects! What about you? Why do you love fireworks?