Answer:
It all comes down to the chemical reaction that happens after the fuse is lit. The burning gunpowder releases hot gas that expands rapidly; when the gas expands to the point that it runs out of room within the firework, the resulting explosion causes a blast wave.
The vibrations from that blast wave have the potential to cause permanent damage to the delicate hair cells of the inner ear.
At close range, fireworks are typically between 150 and 175 decibels—well above what's safe for your hearing.
5 ways to protect your hearing
1. Keep a safe distance
One way is to maintain a safe distance from the display. The farther you are from the sound, the less harmful the sound is to your ears, so your distance from the sound of the fireworks can make all of the difference in terms of decibel level and hearing safety. A distance of around 500 feet will still give you a great view, but without the sound pressure that can damage the tiny hair cells in the inner ear.
2. Skip the home displays
Where you view your fireworks can also affect your hearing. Experts recommend attending a community display rather than setting off your own fireworks at home. Not only are fireworks dangerous and best left to trained professionals, but there is usually a roped off area located a safe viewing (and listening) distance away from the show.
3. Bring—and wear!—earplugs and earmuffs
If you intend to sit as close to the action as possible, or if you are determined to create your own display, protect your hearing and that of your children. Inexpensive foam earplugs can be found in drugstores and pharmacies, and work well for adults; earmuffs (basically foam-filled cups that cover the ears) are better for small children because earplugs sometimes don’t fit and can be a choking hazard.
4. If you buy your own fireworks, buy these
If you are planning your own fireworks display, the good news is you can customize your selection for reduced noise. All fireworks come with a noise level rating, so selecting quieter fireworks will not only preserve a good relationship with your neighbors, it will protect your hearing as well. Quieter options include fountains, wheels, falling leaves and comets. While not completely silent, they crackle and whistle instead of creating a loud, explosive boom. All are created for spectacular visual display but less noise. If you buy fireworks, your fireworks provider should be able to direct you to those that are lower on the noise rating scale.
5. And avoid these
What to avoid? Rockets, mines and any fireworks that have many blasts strung together tightly. These fireworks are created to make as much noise as possible.
Hope this helps, have a nice day/night! :D