Fireworks are, by their very nature, quite loud. How loud they are, however, depends on a variety of factors. In general, commercial-grade display fireworks are louder than the consumer-grade fireworks you can buy for home displays. In addition, some fireworks are manufactured primarily for their display properties, while others are built to maximize the boom. Even atmospheric conditions play a role, making the exact same fireworks sound louder on some nights than others. To understand how all the different factors work together, it is necessary to understand a bit of the science behind the sound.
What Makes Fireworks Loud?
The gas and heat buildup inside a fireworks shell causes an explosion that creates a blast wave, releasing several kilojoules of energy all at once. The blast wave causes particles in the immediate vicinity to follow a particular waveform pattern known as the Friedlander Waveform. Immediately after the explosion, the area around it is over-pressurized, causing compressed air particles to travel faster than the speed of sound. This waveform quickly decays, resulting in a period of negative pressure known as rarefaction.
Loudness is determined by the intensity of the sound, which is proportional to the square of the peak amplitude of the waveform. In other words, the power of a sound wave is proportional to the pressure squared. Increase in loudness is measured through a more complicated formula, but the result is expressed in decibels.
What Are Decibels?
Decibels are used to explain how loud a particular event is. The softest sound that a typical human can hear is 0 decibels. Experts agree that hearing loss can occur at just 85 decibels, depending on the length of exposure. Most people experience sounds of 100 decibels or higher as very loud, and those of 120 decibels or more as painful.
Human conversations are generally between 55 and 65 decibels. Average TV or radio volume is around 70 to 75 decibels. Power lawn mowers, nearby motorcycles, and low-flying jets are approximately 100 decibels. Rock concerts often exceed 115 decibels, and military jet takeoffs from an aircraft carrier are around 130 decibels.
How Loud Are Fireworks?
Depending on their construction, fireworks often exceed 150 decibels, and those that reach 175 decibels are not unheard of. However, this is the peak volume at the point of explosion. Commercial fireworks, which reach high into the sky before exploding, transmit a much weaker sound to viewers on the ground. Consumer fireworks, which explode very close to ground level, typically have a lower maximum decibel level but can actually sound louder.
Fireworks Hearing Safety
Since the decibel level to which you are exposed varies according to how far away you are, it only makes sense to step back several feet after lighting a consumer firework. The World Health Organization recommends that adults be exposed to no more than 140 decibels, which can be achieved by repositioning yourself a bit. Keep children well away from the spot where the fireworks will explode, as they should be exposed to no more than 120 decibels. It is best to keep infants away altogether, as they are highly sensitive to the physical effects of sound pressure.
The length of exposure also matters. In general, you should expose yourself to 85 decibels for no more than 8 hours, and the allowable exposure time is cut in half for every three decibels over 85. So lighting off a few fireworks over the course of an evening isn’t likely to cause much damage if you stand back, but if you test fireworks for a living, you really need to be wearing ear protection.
Denser air contains the blast wave, while high humidity transmits sound waves more efficiently. In addition, temperature inversions, in which colder air sits below warmer air in the atmosphere, can dramatically increase the blast wave. Therefore, the same fireworks can sound louder or softer from one night to the next.
Increasing the Perceived Loudness
If you want your fireworks to sound particularly loud, choose those that have multiple blasts strung tightly together. Although each individual blast wave is not any bigger in these fireworks, the rapidly repeating waves create a longer sound effect that is perceived as louder.
Avoid the temptation to purchase commercial-grade fireworks in an effort to create a louder boom. They are highly controlled and regulated, and you could be subject to stiff legal penalties. Check your local ordinances as well as federal and state law, as some areas have more restrictive limits.
At Dynamite Fireworks, we don’t only sell top-quality, name-brand fireworks. We also provide the information you need to know to use them responsibly, legally, and safely. If you have any questions or concerns, give us a call at (219) 937-4090. We look forward to becoming your one-stop shop for all your fireworks needs!