G&A Basics: The Science of Hearing Protection
August 22, 2013
It is estimated about one in 10 Americans has hearing loss that affects the ability to understand normal speech. The most common cause of this condition is excessive noise exposure. It just so happens shooting firearms is a popular activity that subjects its participants to noise levels intense enough to cause permanent hearing loss, unless the proper precautions are employed.
But how loud can a gun really be? It varies some depending on the firearm and ammunition used, but the sound is more intense than one might think. If we were to measure the report of a rifle, the sound would be checked for the following:
- Frequency: from low to high sounds, measured in hertz.
- Duration: how long the report lasts.
- Intensity: how soft or loud a sound is, measured in decibels (dB).
It's important to note when sound levels are represented in decibels, the increase in sound intensity is expressed in a logarithmic scale. The softest audible sound (near total silence) is represented as 0 dB. A sound 10 times more powerful is 10 dB. A sound 100 times more powerful than near total silence is 20 dB. A sound 1,000 times more powerful than near total silence is 30 dB. This means a change in volume from 150 dB to 140 dB is a more significant reduction in noise intensity than reducing 50 dB to 40 dB.
To clarify how loud a sound measured in decibels can be, it's helpful to have some everyday sound comparisons to work with. Normal conversation occurs at 60 dB. Lawn mowers run at 90 dB, a jet engine at 140 dB, and the noise on a rocket pad during launch pushes the top end of the scale at 180 dB. So where does gunfire land in the lineup? When a gun goes off, the report slams into bare eardrums at 140 dB or more.
Some are incredulous at this revelation, saying there is no way a gun is as loud as a jet engine. However, they are confusing sound duration with sound intensity. The sound of a gunshot only lasts for a fraction of a second, but in that short time, it's very loud.
How Much Can the Ear Take?
So what level of sound intensity is too loud for the human ear? Most experts agree you would have to be exposed to eight continuous hours of noise at 85 dB to cause permanent hearing loss, but sound spikes of 130 dB or more can cause permanent damage instantly.
This means every shot fired has the potential of damaging the ears of anyone within close hearing range. Again, there will be more incredulity at this information, since readers will say they've heard loud noises in the past and can still hear just fine. Here are two important things to remember:
- The various tissues of the human body do not respond to duress in the same way
- Permanent hearing damage can go unrecognized because it is cumulative in nature.
The human body contains an amazing variety of systems, each with specialized tissues to fulfill different tasks. Muscle tissue, for example, can become stronger after being strained. The first time you try a new physical activity (rock climbing, surfing or ballroom dancing, for example) muscles that have not been used quite that way before will become sore and tired. If the activity is continued over time, the muscles will adapt and become stronger. Eventually you will be able to continue those activities without becoming sore like you were the first time. In other words, our muscles adapt and become stronger.
However, the specialized tissues of the nervous system, including brain functions and hearing, do not respond to abuse by rebuilding themselves to become stronger. Instead, when they take enough abuse, they lose their functionality for the rest of a person's life.
For example, think of all the professional boxers over the years who were amazing athletes in their prime, but were left with crippling brain damage by the end of their careers. They successfully toughened their muscles to Olympic-competition levels, but their brains slamming against the interior of their skulls with each blow taken to the head caused irreparable harm. It doesn't usually happen in a single fight, although it can, but brain damage adds up over time. It's exactly the same process with hearing loss. Each loud sound, whether in short or sustained bursts, is like a punch to the ear. It may not seem like a big deal at the moment, but it adds up over time.
Because hearing loss is painless and gradual, it can go unnoticed until the loss, or related symptoms, are quite severe. Many people think losing hearing is like turning down the volume on a television set; all the sounds get softer and softer until you hear nothing at all. That's not the case, especially with noise exposure. What loud noises can do is punch holes in your hearing at certain spots along the frequency line. I know one sportsman who was shooting a particular gun almost every weekend for several seasons without hearing protection. When he did get his hearing checked, sure enough, along with some general hearing loss he had a gap (i.e., deafness) right at the sound frequency produced by his gun and ammunition combination. Ears do not get tougher with exposure to noise; they just stop working.
Besides hearing loss, there's the symptom of tinnitus. From the Latin word for "ringing," tinnitus is the perception of a sound when no external sound source is present. Don't panic if you've had a little ringing in your ears at some point, that's normal. However, if you are around noise loud enough to cause your ears to ring, it's a good indicator that your hearing is in danger of damage. If enough damage is done, the ringing may not go away.
How to Protect Your Hearing
So how exactly should shooters go about keeping their ears safe? The obvious answer is to use hearing protection devices like sound muffling earplugs and earmuffs. These items should have a sound-reduction rating on the package shown in decibels (e.g., 21 dB, 30dB). The higher the number, the more noise they block.
But if guns make 140 dB of noise, how is a 30 dB plug going to help? First, the noise tends to travel forward of the muzzle, so the shooter's ears are not always hit by as much noise as the gun produces. This does not mean the level of sound is safe, only reduced. Second, the purpose of hearing protection devices is not to eliminate sound, but to reduce the impact to a level that does not cause lasting damage. In short, a plethora of scientific studies conducted over many years show hearing protection works, and it works at the sound-muffling levels common devices provide.
With hearing protection so high on the must-have list these days, most shooting ranges will have some form of hearing protection on hand for their customers. Hardware stores and gun stores also have a variety of options in stock. The cheapest form of hearing protection at pennies apiece are the disposable foam earplugs, which usually provide somewhere between 25-31 dB of hearing protection. Reusable rubber-type plugs are also available, ranging from $5-15, depending on the make and model.
The next step up from ear plugs are the ear-protecting muffs, which have the advantage of being reusable for years. The basic clamp-over-the-ear units can run from $10-40, providing the same 25-31 dB levels of hearing protection as the foam plugs. A popular option in really noisy areas like the indoor ranges is to use both plugs and muffs. This is a good idea, but understand the limitations of this system. A 30 dB plug and a 30 dB muff together do not provide a cumulative 60 dB of hearing protection. Instead, they each act as a separate barrier the sound must travel through successively. Hearing protection is improved, but not to as high a level as one might think.
Finally, there are electronically-enhanced hearing protection devices, including specialized hearing aid/earplug combinations, and earmuffs fitted with external microphones and internal speakers. The sound system in electronic muffs allows the user to hear surrounding sounds at a normal levels, or even louder than normal. When a dangerously loud sound is detected by the electronics, the speakers to the ears are deactivated until the noise reaches a safe level again. Prices for these systems range from as little as $50 to thousands of dollars, depending on what you're looking for.
A Personal Matter
When I was approached by Guns & Ammo to write this piece, I hoped they wanted me on the job because of my witty prose and unquenchable enthusiasm for shooting. But in the end, they just wanted me for my body. You see, I have a moderate-to-severe bilateral hearing loss of over 60 dB in the 500 to 2,000 hertz range, along with symptoms of tinnitus. That means I wear hearing aids in both ears to help me understand what people have to say, and I have ringing in my ears.
My hearing loss is genetic in nature, which means there was nothing I could have done to avoid it. It's a little gift from my DNA that kicked in about 17 years ago, but the symptoms are just the same as those caused by loud noise exposure. I was careful to protect my hearing before the loss, but I'm religious about taking care of what I have left now.
Is the Tinnitus annoying? Yes, on good days it's only annoying. Do I miss hearing and understanding what my wife, kids and co-workers have to say? Only when they choose to speak to me. Don't the cutting-edge digital hearing aids help? Yes, and they're a real bargain at $1,400-3,000 apiece, plus the cost of replacement every three years or so, batteries, maintenance, service charges, and hearing checks.
While it may be better to have loved and lost than to never have loved at all, I just can't come up with any reason why losing hearing would be plus. Ear protection is far too easy to obtain and use for anyone to have a good reason to gamble with their hearing. So what is your hearing worth? The last I checked, you can start protecting it for as little as 25 cents (foam plugs) per trip to the range. Take it from me, it's well worth the investment.