My Account/ Know How / Tools /

Know how Hearing Protection is used and its Importance

Courtesy of Dan Kerr.

As I worked on the farm with various tools, my concern for hearing protection drew me to look up Patricia Van Hoof, through our local hearing society. Van Hoof is an audiologist in Sault Ste. Marie, with offices in Blind River and Elliot Lake. Van Hoof is a graduate of the University of Western Ontario with her Masters in Audiology, and upon request, attended my farm for some testing.

Upon arrival I displayed my collection of hearing protection, all of which are the muff variety - or circumaural, as the professionals refer to them. There were some markings on the muffs which I questioned about, none of which made any reference to audiology at all. If the equipment is approved, it will display the Underwriters Laboratories logo and its Noise Reduction Rating (NRR). NRR is what the equipment is rated at, which is interpreted by the following:

  • if the rating is 30 and you are subjected to a noise level of 90, your actual exposure would be 60 dB of sound. You subtract the rating from the actual level.

The allowable steady noise level for an eight-hour time as set out by the Canadian Federal Noise Regulations is 87 dB. Quebec allows 90 dB and all other Provincial regulations are 85 dB.

As there are numerous choices in design, I asked for her preferential rating: "I prefer custom hearing protection, which are expensive and have to be personally made from an ear mold impression to fit the ear canal. They allow conversation to be heard but block out loud sounds up to 24 dB of reduction. This allows the protection to be fitted at the start of a job and removed at the end, rather than constantly fitting and removing throughout the day" Her next choice are the muff type, which are also available, fitted with similar electronics allowing conversation to be heard while blocking out loud noise. These are commonly used by shooters, and do not require any custom fitting. Her last preference is the ear plug type, which rarely are fitted properly, and if removed and refitted, allow the risk of contamination entering the ear canal.

I have a collection of the standard muff type and have found that they almost all differ in comfort and fit - and that the strongest and best fitting of these have a metal band holding them in place.

The collection of muffs that I have are spread out, hanging in the welding shop, a designated pair in the tractor, attached to my arborist helmet and on all of my woodworking equipment, so there is no excuse for me not to wear it. This is cheap insurance to prevent the development of deafness and having to purchase hearing aids down the road, which are significantly more expensive than a shop full of earmuffs.

The inscription on my earmuffs turned out to be manufacturing notes, and there were no NRR indicated. Van Hoof advised that if the manufacturer indicates the NRR on the unit, they can be held accountable. As all equipment is tested under laboratory or ideal conditions, it is impossible for a manufacturer to know if their safety equipment is being worn or fitted properly. For example, are muffs placed over the arms of glasses or a hat or both? Any of these situations would significantly alter their effectiveness.

Van Hoof brought with her a decibel meter, and she put it to the test on the inside of my tractor cab. Outside, with the engine at 1500 rpm (which is close to where I run it), we took readings which confirm my original observation:

  • outside cab = 78.0 dB

  • inside cab door closed = 85.4 dB

As I am commonly in the cab cutting grass for 4-hour durations, the earmuffs will provide adequate needed hearing protection.

Note that when you add equipment, you add more decibels to the equation - so instead of being on the border for my tractor, it would put the decibels well over the limit.

The cab is also a factor. The harder/smoother the surface, the less sound it will absorb, so it reflects and then reverberates, producing a louder environment. Blown foam, plastic covered fiberglass ceiling tiles and egg cartons are three products that I have used over time to deaden noise: they all work well, are light, easy to find, easy to work with, and cheap to acquire.

The tractor isn't the only thing I use around the farm, so while I had a dB meter on hand, I tested a few other tools:

  • shop vacuum=74.8

  • shop vacuum as dust collector and radial arm saw=94.4

  • both while cutting wood=98.6

  • air angle drill just running=101.2

  • handheld 5" grinder just running=93.0

  • air sheer just running=102.3

  • 7 ¼" skill saw just running=97.7

  • air compressor=102.0

With just these few you can see that all but one is over the 85-dB limit and remembering that each time you add a variable or workload along with the tool you add to the dB rating, the numbers add up.

A friend of mine advised that the color of the muffs indicate their dB rating. This is not so. Color has no bearing, other than a manufacturer's or consumer's preference. The muffs that I purchased had a 25-dB rating on the packaging, which is typical. At the end of the day, it's the dB rating that makes one pair better than the next, not the color.

The only piece of equipment that doesn't have muffs hanging on it is my floor belt sander, which I turned on before fitting my muffs one day and the sander ate them! W

Dan Kerr learned photography in his dad's darkroom, then progressed to providing photos and articles for magazines, and crime scene photographs for the Ontario Provincial Police, as a forensic identification officer.