When I purchased and installed a second hand cab on my Kubota B7200 I was thrilled — I now had protection from sun and cold. But what I didn’t count on was the increase in noise.
In the profession of audiology, noise is referred to as decibels (dB) which are the units to measure sound pressure levels (SPL). SPL is the perception of noise in humans as it can be “read” by our ears.
It wasn’t too long after the cab installation that I noticed a ringing in my ears, and soon after that hearing protection (HP) was part of the safety equipment needed in the cab.
Several questions came to mind with this scenario so I located Patricia Van Hoff through our local hearing society. Patricia is an audiologist who has offices in Sault Ste Marie, Blind River and Elliot Lake and also travels along the north shore to patients who can not attend the office. A graduate of the University of Western Ontario for her Master in Audiology, Patricia attended my farm for some testing.
I showed her my selection of hearing protection which is headphone type (or circumaural as the professionals call them) and asked her what the markings on the side meant.
Answer: If the protection is approved it will have the Underwriters Laboratories logo along with the ear protections Noise Reduction Rating (NRR). The NRR is interpreted as follows: if the NRR was 25 and you were to be exposed to 100 dB of equipment noise, you would be subject to 75 dB of sound. The Canadian Federal Noise Regulation permitted allowable steady noise level for an eight-hour work shift is 87 dB. All Provincial Regulations are 85 dB except Quebec which is 90 dB.
As for choice, Patricia advised: “I like the custom hearing protection, but these can be costly and require an ear mold impression to be sent to the manufacturer to be made specific to fit your ear canals. They have filters in the canal portion so that conversation can be heard but then closes when loud sounds enter so that you receive the benefit of up to 24 dB reduction. The option of hearing conversation without removing the ear protectors means that you do not have to continuously remove and put the ear protectors in over and over throughout the day.”
Her next choice is the headphone type that I have and her least favourite is the ear plug type which as she says “rarely fit properly or are effective.” I like to try on the phones prior to purchase as there seems to be a huge difference in comfort and fit. I have also found that the units with a metal strap fit more snugly and are more resilient as opposed to the plastic ones.
I have several pairs of protectors hanging on various pieces of equipment throughout my shop — a pair in the welding room, a designated pair in the tractor and an attached pair on my arborist helmet so laziness cannot intervene prior to machine operation. These are cheap insurance to prevent the onslaught of deafness and ultimate acquisition of hearing aids, which are somewhat more expensive than headphones.
Much to my chagrin, when Patricia checked my collection of protectors none had a NRR indicated on them. When questioned she advised that if a manufacturer indicates the NRR on the unit they can be held accountable and as it is almost impossible for any manufacturer to know how their product is being worn its no wonder they don’t indicate it on the unit as the variables are unlimited. The manufacturer’s testing is done in optimum conditions with new, clean, properly fit units. Once out in the field those parameters change.
With the use of her dB meter I had Patricia monitor the dB rating on my tractor while it was idling. The results were interesting:
--beside the tractor: 78.0
--inside the cab, door closed: 82.0
I then increased the engine speed to 1500 RPM which is my most common operational speed and tested again:
--beside the tractor: 81.5
--inside the cab door closed: 85.6
This is clear affirmation of my decision to wear ear protection. The dB registered is slightly over the maximum provincial allowable rating for an eight hour exposure. A note here: when you add equipment such as a mower the dB will increase.
The harder a surface, the less sound it will absorb. The sound reflects and reverberates together to create a louder environment. Sound absorbing materials have a data sheet indicating their rating. I have used pieces of poly coated fiberglass ceiling tiles, styrofoam and in one application egg cartons, which are fantastic, easy to obtain, light and cheep.
While I had her on the farm I had Patricia rate some other equipment that I often use:
--vacuum=74.8
--vacuum and radial arm saw=94.4
--both while cutting wood=98.6
--hand held 5” grinder just running=93.0
--1/4” drill just running=83.4
--7 ¼” skill saw just running=97.7
With just these few you can see that all but two are over the 85 dB limit and again, each time you add a variable or work load you add to the dB rating.
I often thought that the colour is an indication to the dB rating but not so, colour is a purchaser or manufacturer choice and has no bearing on the dB protection provided. Although my headphone protectors are not rated they do dampen the dB as well as keeping debris out of the ear canals and I figure, something is better than nothing.
Patricia laughed when she read the fridge magnet on my tool box that says, “I’m not hard of hearing, I’m ignoring you”; she then advised me that I do have a hearing loss. As it turns out, my frequency loss is exactly the same as the female voice.
For every negative there’s always a positive!
- Dan Kerr