It’s time for a serious talk about ear protection! For a long time as a hobbyist, I was fairly lackadaisical with my hearing protection for woodworking purposes. If I needed to make a quick cut with the circular saw or do some pruning with a recip, it was often the last thing on my mind to grab the earmuffs from the shed. In addition, over the course of my time perusing the web for different ideas or tutorials I have seen countless videos and pictures of people operating heavy power tools without any ear protection.
There are a lot of things around this mid-life era where I’m at now that, looking back, I would do differently. I don’t want not wearing ear protection to be one of them. Which got me to thinking about a lot of the questions that I’ve heard – what level of protection do I actually need when using my tools? Am I even doing enough work to risk damaging my ears? Are noise-canceling earphones enough? This led to an OCD level deep dive into the research behind ear protection and dangerous noise levels.
So, if you want to know about hearing protection and don’t want to spend the hours and hours of time that I spent to understand it, here’s my summation of everything you need to know about hearing protection for the woodworking crowd.
How is sound measured?
When I began digging around to find what was an adequate amount of protection, I first had to find out how noise is measured and what a dangerous level of noise was – I mean, my dog , Taco, has a pretty loud bark, do I need protection for that too?
In the simplest terms, sound is measured in regard to its intensity or volume, which is measured as decibels. The decibel scale measures from 0, or the lowest sound our ears can pick up, to 180dB – which is the sound measured from the launch pad of rockets.
An important thing to know when considering hearing protection is that decibels are measured on a logarithmic scale. Unlike linear scales, where the value between any two points is always consistent, logarithmic scales rely on exponents.
For decibels, every 10-decibel increase equates to 10 times the corresponding lower number. 30 decibels is, therefore, ten times louder than 20 decibels and one hundred times louder than 10 decibels.
The A-weighted scale
In terms of hearing protection, we regularly use an “A-weighted” decibel scale (dBA).
Think of all the times you wanted your test scores bell-curved, and you’ll get a bit of an idea of what dBA is. Essentially, it takes into account the various factors related to how the human ear processes sound and frequencies. Because our ears have trouble picking up very low and very high-pitched sounds, A-weighted decibels and the machines that are calibrated to them, specifically measure for the range of sounds that our ears are actually sensitive to. That’s why dBA is used as the primary measurement for environmental noise and hearing protection. It’s meant to be as accurate an interpretation of what our ears are truly hearing that the current research can get. When you see the safety warnings for certain levels of noise under The Occupational Safety and Health Regulations (OSHA) they have always been measured as dBA.
What is a dangerous decibel level?
The risk of hearing damage in relation to noise levels has several variables. How loud the noise is, how long you are exposed to it, how much time your ears are given to rest between exposures, and your individual vulnerability to noise all play a factor in what a dangerous noise level is for you.
However, the Centre for Disease Control has listed a recommendation that anything over 85dBA should be considered levels of noise that are potentially harmful for hearing loss, and efforts should be taken to reduce the noise, wear protection, or limit exposure to it.
To determine what level of hearing protection you need, you need to know what dbA your specific environment is putting out, and the amount of time you will be exposed to it.
(For the purpose of this article from now on when I refer to ‘decibels,’ they are always A-weighted or dBA)
The recommendation is that any time you are exposed to noise over 85 dBA, you should wear ear protection. In addition, you should never be exposed to any noise level over 140dB (as heard in gun shots and explosions – such as fireworks) as this amount of noise can cause nearly instant permanent damage. (I can see now why my poor dog, Taco, is so averse to fireworks!)
To put dangerous levels of noise into a more day to day perspective, if you listen to your headphones at full volume it can often exceed 100 decibels, which is enough to permanently damage your hearing within only fifteen minutes of exposure!
And look, I know we don’t all have the equipment to measure the sound level of our environment but if you are having to raise your voice to be heard from one meter away, or if a specific noise hurts/makes your ears ring then the noise may be capable of damaging your hearing. So, it’s always better to be safe than sorry!
What dBA are my tools putting out?
Now that we know what a decibel is and how sensitive our weak, little human ears are to them, we can take a look at what some of our more common woodworking tools are putting out.
In a study titled “Noise Levels of Common Construction Power Tools,” written by Gregory Callahan of the University of Florida, a Porter Cable circular saw came in at a decibel of 92.7 when measuring its noise level from the ear level of the operator in the centre of a room.
So, we can clearly see that our power tools have the capacity to be well above the safe decibel level!
An interesting note in this study also showed that using power tools in enclosed spaces, or in the corner of rooms dramatically increased the recorded decibels (in the case of the Porter Cable saw it was up to and over 114 decibels when measured in the corner of the room!) This was chalked up to the amplification of the room and the soundwaves bouncing off of close surfaces. This means that, when you have the option to use your tools in an outdoor space, it’s measurably better for noise reduction.
Most sound information I have found on power saws and planers puts them in the 100+ decibel range.
The answer then to “do I need hearing protection for my power tools?” is yes. Every time. Exposure to noise and the damage that it causes builds up over time, and there really should be no reason to risk your future hearing for your laziness today. (Giving my former self a hefty slap on the wrist for that!)
What is adequate hearing protection?
We know that our tools can put out enough noise to be harmful, so what are our hearing protection options? In order to get to that, we have to know about the regulated rating system that is used to determine the effectiveness of each piece of hearing protection.
Noise Reduction Rating (NRR)
If you’ve done any shopping for ear protection you’ve probably come across the acronym NRR, which stands for Noise Reduction Rating. NRR is a standard of measurement, developed by the Environmental Protection Agency, which determines the adequacy of hearing protection to perform its desired purpose – sound reduction in a working environment.
The higher the NRR the better the noise reduction; and therefore, hearing protection that the specific product will provide. The highest current NRR measured in a product is 33dB
How is NRR determined?
The NRR that you see on the labels of all regulation hearing protection is calculated in a laboratory under very controlled settings. The test is the same regardless of where it is done. The NRR rating is calculated based on the average amount of reduction in noise that is provided by the hearing protection device when test fitted to at least ten different people, who are each tested at least three times. These ten different people don’t put the hearing protection on themselves – instead they are fitted by the laboratory team.
The above fact is important to note and is the reason that you can’t take NRR at its face value, because research has indicated that the laboratory results severely overestimate the actual real-world effectiveness of the device.
And that, my friends, is why we unfortunately have to do some math.
Because the number seen on the NRR rating is the maximum
level of decibel reduction that was seen in the laboratory setting with ideal conditions, under the circumstances where the product is perfectly fitted and worn correctly, and with no outside environmental effects, we can’t just use the NRR number to calculate the total protection we are getting from a specific product in the real world.
For instance, if your hearing protection has a rating of NRR 25dB and the noise level of your environment is 95dB – wearing your ear protection doesn’t result in a decibel level of 70. To account for real-world conditions there is an equation we can use to determine an adjusted number that is a more accurate representation of the decibel reduction you may expect from your hearing protection.
To get the actual decibel reduction for the hearing protection you subtract 7 from the NRR rating and then divide the result by 2. This number can then be subtracted from the environmental decibel rating.
Ex. NRR of 25dB and environmental rating of 115
(25-7 )/2 = 9
115-9 = 106 is the adjusted decibel level when wearing the protection.
NRR Subject Fit (SF)
Because of the variance that can be seen in the laboratory testing to real-world environments, new testing parameters have been introduced in some areas. In these tests the subjects themselves, as opposed to the testing staff, fit the protection. In this way, some of the variance of user error is omitted from the test.
NRR (SF) is now used in Australia, New Zealand, and Brazil and is OSHA compliant as a new rating system that doesn’t require the above calculation corrections (No math, yay!). So, if you see an NRR (SF) label, you can subtract the number directly from the decibel rating of the sound you are trying to protect yourself from.
What protection should I wear?
Good question! If we know that many power tools can reach the 100dB range, we should be finding ear protection that is at least NRR29 which, given the above adjustments, would bring a 100dB sound down to approximately 89, and then doubling up with both in-ear and over-ear to bring that down further.
Unfortunately, doubling up protection doesn’t actually double the amount of protection. While there is conflicting information on the exact amount of added protection you gain from doubling up, most research simply adds 4-7dB of added protection to the NRR rating.
Which certainly does help, but not as much as you may have thought! Even so, leading health organisations suggest doubling up anytime the expose is over 105db.
This means, when you are using tools such as a table saw that can regularly go over 105dB, you should be doubling up for safety. Especially if you are using it for long periods of time.
And as for my earlier question of whether audio earphones were enough? I’m sure, at this point, you know the answer is no! Not only do they typically not provide enough protection, oftentimes people will up the volume in order to hear their music above the sounds being generated around them – which is dangerous in itself!
How to wear protection?
As always, a piece of equipment is only effective if it is used in the way it was intended. Research has indicated that up to one-half of people who use hearing protection are receiving half or less of the potential NRR rating listed on their device. This is due to improperly fitted equipment as well as the protection not being worn continuously throughout the noise exposure.
Improperly fitted equipment won’t create a full seal and therefore will not protect against dangerous noise levels. This is why it’s important to always follow the appropriate instructions provided when fitting your chosen hearing protection! If you are wearing earplugs a handy way to check if your fit is proper is to place your hands over your ears – if the plugs are fitted correctly the noise level should not significantly change when you do so.
Over-ear protection should form a full seal around the ear. Glasses or long hair can easily get in the way of this and ruin the level of protection provided.
Lastly, it’s important to keep the protection on for the duration of the activity that you are protecting yourself from. Removing it even for a short while can drastically reduce the protection level for the entire time you are using it. Crazy, eh?
What does this mean for woodworkers?
It means that every time you reach to turn on the saw or spend some time with the power sander, you should also reach for the ear protection, and the ear protection you reach for should have adequate NRR and be properly fitted. We know from research that every exposure to dangerous decibel levels, no matter how long, can eventually add up to a permanent hearing loss.
It also means that I have something to say to a lot of the very popular crafters about their videos and pictures which lack hearing protection:
You have a platform that is widespread, and a reach that requires you to hold yourself to a certain standard. By portraying yourself as an expert in your field, and by not practicing safe measures you are insinuating to your followers that it isn’t necessary for the hobby woodworker to make the effort to pull on a pair of ear protection before cranking up the saw. I really don’t want to have to start yelling at the next generation of hobbyists because they followed your example and now, instead of choosing not to listen to me, simply can’t hear me.
So, wear your PPE friends!
This has been a friendly neighborhood PSA from your truely.