Cashins & Associates Blog

Industrial Hygiene: Quantitative Assessment of Hearing Protectors

Posted by Timothy Aeschliman on Tue, Jul, 07, 2015 @ 14:07 PM


A recurring challenge for industrial hygiene and safety professionals is personal protective equipment and the human factor in its use. Companies assess noise exposures, provide medical monitoring and personal protective equipment, provide training and conduct workplace observations and audits; yet occupational hearing loss continues to occur. What else can be done? Recently, I tested out a quantitative ear plug testing system that evaluates how well ear plugs fit and learned quite a bit about the practical limitations of ear plugs.

As with most equipment, I had to first familiarize myself with the software and hardware setup, so I elected to test myself before I asked for volunteers.  The principle of operation of the equipment reminded me of the TSI Portacount; the microphone basically compared noise levels inside the ear canal to levels in the outside environment. A small speaker provided the test signal, and the software took care of the analysis and reporting. Several different styles of earplugs were available to choose from, depending upon individual preference.

Some things I learned by running myself through the test.

  1. My first choice in earplugs was not the best choice; my right ear fit well and my results (33dBA) reflected that; my left ear (17 dBA) wasn’t even close. No matter how many times I attempted to re-fit my preferred ear plugs, I could not improve the attenuation in my left ear.
  2. I have two different sized ear canals –the left is larger than the right.
  3. With any earplug, I have to work much harder with my left ear to ensure I get a good fit.
  4. I could only tell a difference after I selected another set of foam plugs, and went through a re-test. Only then did I come close to the rated performance of the ear plugs for both ears.

Four out of five (80%) of the employees I subsequently tested with the equipment experienced similar differences between their left and right ears, and all benefited from changing earplugs. Only one person made it through the evaluation without any additional adjustment.  

So the obvious question is: Do all employees need a perfect fit and maximum attenuation from their earplugs or earmuffs?  The noise levels and duration of exposure at your site will dictate the answer. The primary benefit of the test results was that it provided a teachable moment with each employee and permitted changes that either improved their individual level of protection, or provided them with a better understand of the limitations of the earplugs they selected. I personally could not detect any difference between my right and left ear during my first test, which revealed a difference of 16 decibels (33, 17).

I came away from this exercise impressed with this type of quantitative test equipment and the benefits it affords employees who are exposed to noise. While it certainly isn’t a necessity for everyone, it’s good to know that it’s an option.

Photo Courtesy of 3M Corporation:


Topics: hearing loss

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