Hearing Protection in the Woodworking Workshop

First things first. There is a HUGE range of hearing protection out there. (BTW, I don’t say ear muffs, as we had a definite opinion about what ear muffs were in the navy, and it wasn’t hearing protection, and it never got cold enough to actually wear “ear muffs”) The question has to be asked however- does the choice really matter? After all, wouldn’t wearing hearing protectors, irrespective of type leave you better off than you are without any?

Unfortunately, the answer is definitely no. It is imperative that you choose hearing protection designed for the type of noise that you are expected to encounter. To give an example, hearing protection for firearms is useless in a workshop environment. It is specifically designed for a momentary peak noise, not long hours of high frequency, loud noise. To wear the wrong type leaves you thinking you are protected, with normal frequency sounds blocked, while the damaging high frequency sounds, such as made by a router goes about its ‘job’ of wrecking your hearing.

So what are we looking for in hearing protection for the woodworking workshop environment?

  • Comfort. after all we will be wearing them for moderately long periods of time.
  • Compatibility with other safety equipment. Because of the material we work with, eye protection & lung protection is mandatory, so all three must go together without compromising comfort or protection.
  • High frequency protection- such as made by a circular saw or router.
  • Moderate volume protection. The circular saw is pretty loud at close range, and will cause hearing loss, but isn’t as loud as some other work environments.
  • Communication potential. The best situation is protection from the sounds that will damage hearing, yet still allow you to hear the person next to you talking. These are not mutually exclusive, as good hearing protection blocks damaging frequencies, while still allowing the sound frequencies associated with speech to pass relatively unaffected through the ear defenders. This would allow us to leave our hearing protection on the whole time we are in the workshop, and not have to continually remove and replace our hearing protection every time someone speaks. There are some with a built-in microphone and speaker, which transmits noise from outside the ear defenders when the noise level is acceptable, and cuts the circuit when the volume exceeds a given point.

One brand that is ideal ones for our environment are Peltor H7 or H9. Peltor H7 is the higher rated of the 2, and only costs $3 more. They are more expensive than the stock ones available from Bunnings, however it is, as always, a case of “you get what you pay for”.

With respect to headband types, the choice is yours, as reputable brands offer their ear defenders with a range of headband. There is the normal headband, the neckband, a collapsible headband, or the hardhat attachment.

So what level of protection do we need?

The following graph demonstrates the amount of exposure time allowed plotted against volume. As you can see from this, you can listen to 85dB for 8 hours, or 100dB for 15 minutes.

volume1.jpg

So how does this relate to ear defenders / muffs?

Ear defenders are rated by how much noise they block. You can buy a 10dB ear defender, 22dB, even a 31dB.

Because of the large range in noise levels that can be detected by the ear, the decibel scale is not a normal scale. Instead, a 3 dB increase in noise level, though barely perceptible, corresponds to a doubling of sound energy. A 10 dB increase, indicating 10 times the energy, seems twice as loud.

The amount of damage caused by noise depends on the total amount of energy received over a period of time, the louder the noise the faster it causes damage. A noise 3 dB greater has twice the energy output and causes the same damage in half the time.

So from this, you can see that an ear defender that blocks 28dB is excellent.

Another way of looking at this is taking the actual noise level of the equipment, and subtracting how much protection the ear defender is providing.

noise.gif

Hours of Protection

noise2.gif

From this, you can see that all this equipment should be used with hearing protection. Damage is cumulative, so even if you only use the saw for 2 minutes, then do another cut that takes 3, the use the router for 5 minutes, and finally the belt sander for 4 minutes, you have suffered a degree of permanent hearing loss. The amount of damage you do next time adds on to this, and so on.

Recommended for our work is ear defenders in the range of 28-31dB

You can buy some cheap ones from Bunnings, such as Protector, which will cost between $15 and $25.

However, my highly recommended brand is Peltor, which will cost $60 for the H9, and $65 for the H7. The cost is the same irrespective of the headband type you choose.

For excellent all-round protection in the workshop, it is hard to go past the Triton Powered Respirator, released onto the market mid 2003. It provides excellent full-face protection, hearing protection and respiratory protection via a positive pressure, open circuit air supply system. Even so, I don’t wear it all the time – horses for courses, and for many jobs it is definitely overkill. On the other hand, on days that I do decide to don the rig, I have a much better sleep that night with my lungs thanking me, in addition to having my eyes safe, and my hearing protected.

tpr.jpg

For your convenience, I have also priced the hearing aid below:

ear.jpg

Cost: $600 – $1000 per ear.

One final word about using your equipment.

High frequency sounds are substantially more damaging than loud low frequency. So beware both your router and circular saw which both generate high frequency sound. The router operating in the 10- 15000 RPM range is very damaging.

Secondly, how you use your equipment has a marked effect. If you push the work through, you can increase the volume of noise you produce by 3dB easily. Doesn’t sound like a lot, but remember that 3dB represents a DOUBLING of the sound energy, and therefore means you will damage your hearing in half the time. (eg 15 minutes when going gently, compared to 7.5 minutes if you force the work.)

So keep safe, and don’t get complacent about your hearing. Thus ends the lecture!

7 Responses

  1. I would add: wear the protectors and leave them on. If you take them off for only 1% of the time you are exposed to noise, the effectiveness drops to a mere 10%. In other words, you lose 90% of the benefit. If you have to take them off to talk with somebody, maybe you are over-protecting. The protector should block out the most damaging frequencies while still allowing the lower-pitched human voice to be heard.
    You point out that woodworking machines & tools make a high pitched noise which is more damaging to our hearing. The diagrams show us that earplugs block more sound in the high frequencies, so a protector which is rated 28dB on average will probably block up to 35dB in the 2 kHz band and even more at 4 kHz.
    It would also be nice, I think, to have a pair of budget muffs hanging around, so you can hand them to visitors.

  2. Some very good points there Marcus – thanks for the input!

    The points about over-protecting leading to poor practice, and having spare sets for visitors are particularly pertinent.

  3. a really good explanation. I’m wondering if a noise cancelling headset will provide even more protection in the wood shop. On an airplane they work really well, but they are cutting out the heavy plane noise which I suspect are lower frequencies than a table saw

    any comments or suggestions?

  4. Hi Bill,

    I have thought about this in the past, and the conclusion that I have come with is: definitely NOT!

    I may be wrong on this, but the noise canceling headset doesn’t have any significant noise blocking capabilities, and instead relies on its ability to produce sound that is out of phase with the actual noise, canceling both out. The noise generator in the headset has to be able to produce sound across the entire frequency range, to sufficient volume to be able to provide actual protection, and I very much doubt if it can.

    They are designed to knock out ambient noise, and volumes, and not necessarily in the frequency ranges of the equipment we use, or with sufficient volume to render the noise down to a safe level.

    That is not to say that the concept wouldn’t work, but I’d only consider it safe if that technology was built into devices specifically designed to protect hearing, rather than deliver an optimum listening environment.

    So theoretically possible, but I don’t know of any device on the market certified to protect hearing in this manner. Remember that you may not really hear the actual frequencies that is actually doing the damage. You may feel safe, and the sound appears all gone, and your hearing is going with it.

    Interesting question though!

    Stu

  5. I believe that the Peltor electronic earmuffs provide an increased amount of safety. They allow me to turn down the sound of the saw, but I can still be more aware of my surroundings. I can also hear my wife yell at me when I have been in the shop too late. My also are combined with an AM/FM radio, the Peltor Alert Radio Earmuffs.

    http://www.envirosafetyproducts.com/product/Peltor-Alert-AM-FM-Radio-Headset.html

  6. Good point, and I hadn’t updated my article here since getting a pair that works in a similar way. The hearing protection is inherent in the earmuffs themselves, and the ambient sounds are picked up by an external microphone and transmitted to speakers in the headset. This circuit has the volume control. When the volume exceeds a certain threshold, that circuit cuts out, effectively turning them into a standard pair of ear protectors.

    In looking at the link, it confirms my suspicion that it isn’t more protection than a standard pair, but the fact that you are more likely to leave them on is still good. The active circuits are not noise canceling (high volume), they simply disengage the circuit when the volume increases.

    They are a good idea, and particularly when I’m running a course – you can leave them on, and still talk / answer questions between cuts.

    (And the marital harmony is worth their weight in gold!)

  7. Hi I was just wonderind if your company has any hearing protection for railroad workers. To protect them self from the noise and communicate with themselves.

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