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The Safety is in the Numbers – Calculating the Right Hearing Protection for Your Team By Brian Pinon

- October 13, 2017 by Brian Piñon, CSP (View all posts by Brian)

In the course of my career, I’ve walked through hundreds of operations utilizing powered equipment producing high noise levels. Most of these organizations offer hearing protection to workers but have not taken the time to quantify their noise exposure or ensure the provided hearing protection is adequate. In this blog, I will explain how to ensure your hearing safeguards sufficiently protect your workers.

All Hearing Protectors Are Not Created Equal

If you’ve ever shopped for ear plugs or muffs, one of the first things you would notice is that they are assigned a Noise Reduction Rating (NRR) in decibels. In selecting hearing protection for their workforce, the most common mistake leaders make, is assuming that an NRR signifies the number of decibels reduced for a particular noise exposure. However, this rating reflects the highest noise exposure reduction that the protector can provide in an ideal laboratory setting.

Due to physical differences between people and how effectively protectors are worn, the actual level of protection afforded to someone will almost always be lower than the listed Noise Reduction Rating.  I recommend using the following OSHA formula as a best practice for calculating the effectiveness of a hearing protector:

(NRR – 7) ÷ 2 = Presumed Reduction in Exposure in Decibels. (dBA)

For example, ear muffs with a listed noise reduction rating of 27 would provide a presumed reduction in exposure of 10 decibels.

(27 – 7) ÷ 2 = 10 dBA

Doubling Up, Doesn’t Equal Double Protection

A second mistake leaders make, is to assume that combining protectors (i.e., wearing ear plugs and muffs) results in a purely compounded noise exposure reduction. The reality is that bone conduction, the transmission of sound through the bones of the skull to the inner ear, produces a decreased effectiveness for the 2nd protector. To account for this reduction, OSHA recommends plugging in the protector with the highest NRR into the formula and adding 5 dBA to account for the second protector.

[(NRRHighest – 7) ÷ 2] + 5 = Presumed Reduction in Exposure in Decibels(dBA)

If you have not yet quantified your worker noise exposure, please contact your ICW Risk Management Consultant for guidance.