“Hearing loss is a terrible thing because it cannot be repaired.” — Pete Townshend
“Why not?”
The young operator had just asked if they could wear earbuds instead of ear plugs when they were out in the process. “I mean, as long as I’ve got something stuck in my ears, it might as well be entertaining.”
I replied that I didn’t think it was a good idea to use earbuds as a substitute for ear plugs, but when they challenged me, I was stuck for an answer. I didn’t want to resort to that parental cliché: “Because I said so.” But I didn’t have a better answer.
Now I do.
What Is A Safe Sound Level?
The term “noise” is a value judgment. It refers to any sound we don’t like.
“Occupational noise” is not. It refers to sound that can cause hearing loss. OSHA has established a permissible exposure limit (PEL) for occupational noise of 90 dB for an 8-hour day. OSHA uses a 5 dB exchange rate, meaning that the PEL of 95 dB is 4 hours/day, the PEL of 100 dB is 2 hours/day, the PEL of 105 dB is 1 hour/day, the PEL of 110 dB is ½ hour/day, and the PEL of 115 dB is ¼ hour/day. There is no permissible exposure to sound levels higher than 115 dB.
NIOSH takes a more realistic approach in establishing sound levels that are safe. To begin with, it uses a 3 dB exchange rate, which is consistent with the definition of decibel (an increase of 10 dB results when the sound level is 10 times greater, meaning that sound levels must be doubled 3.32 times to achieve a sound level increase of 10x. 10 ÷ 3.32 = 3 ) Then it starts with an unambiguously safe sound level for an 8-hour exposure, one that will not result in hearing loss: 85 db. Doubling that sound level 5 times takes us to a sound level of 100 dB, with a safe exposure time of 15 minutes per day.
The point of hearing protection, then, is to make sure that ears are not exposed to sound levels high enough to cause hearing loss.
When Is Hearing Protection Adequate?
Hearing protection is not absolute. Different types—even different makes and models—provide different levels of protection, and no one should believe “I’m wearing hearing protection, so my hearing is safe.” The adequacy of hearing protection depends on both the sound level in the workplace and the Noise Reduction Rating (NRR) of the hearing protection. There are three types of hearing protection: canal caps, earmuffs, and ear plugs.
Canal caps typically have a NRR of no more than 20 dB. This shouldn’t come as a surprise since the caps only rest in the entrance to the ear canal and don’t seal the ear from environmental sounds. This means that it is only in sound environments where the sound level is less than 105 dB or less that canal caps are likely to be adequate.
Earmuffs typically have a NRR in the range of 25 to 30 dB. They are better than canal caps because earmuffs seal around the ear to reduce the amount of sound getting to the ear. Depending on the make and model of the earmuff, they may be adequate to allow an 8 hour/day exposure to a sound level up to 110 dB. A sound level of110 dB is high enough that NIOSH doesn’t consider at all safe and OSHA has a PEL of less than 30 minutes for exposures to 110 dB. Hearing protection at least as good as provided by earmuffs is required.
Ear plugs are the best hearing protection when worn correctly, with a NRR in the range of 27 to 33 dB. “Worn correctly” means inserted completely into the ear canal, so that the outside of the plug is flush with the entrance to the ear canal. When ear plugs are worn correctly, though, they will allow someone to work a full 8-hour shift while exposed to sound level up to 115 dB. At higher sound levels, the exposure time must be reduced, even when wearing ear plugs.
What About Earbuds and Headphones?
When considering earbuds or headphones as hearing protection, the first question to answer is “What is their NRR?” For hearing protection devices, which are tested and certified as hearing protection devices, the label on the package has this information. For earbuds or headphones, the information is simply not available. Why? Because the manufacturer never intended them to be used as hearing protection.
We can’t just assume that earbuds will act like ear plugs, or that headphones will act like earmuffs. Ear plugs are designed to expand and fill the entire ear canal, sealing the ear. Ear buds are not. Likewise, earmuffs are designed to form a seal around the ear to keep out sound. Headphones are not. That is not to say that there is no noise reduction from earbuds or headphones; there probably is some. It’s just that we don’t know how much (although it is probably very little) so we have no way to judge their adequacy.
What About Noise Cancelling Devices?
There is technology available that uses microphones to detect the waveform of incoming sound and produces a wave that is 180° out of phase, cancelling the incoming sound. Bose introduced the first commercially available noise-cancelling headphones for aviation in 1989 and offered the Quiet Comfort model for the general consumer in 2000. Today, several manufacturers produce noise-cancelling headphones. However, “most consumer-grade active noise-cancelling headphones are not tested or certified as hearing protection.”
That doesn’t mean that noise-cancelling headphones haven’t been tested at all. A recent report summarized data for ten noise-cancelling headphones from four different suppliers (Apple, Beats, Bose, and Sony). The amount of noise reduction ranged from as low as 13 dB to as much as 30 dB. However, they weren’t tested according to standard protocols and none of these suppliers make any claim for their products as hearing protection.
However, even if they worked as noise reduction devices, they are able to play louder than 85 dB. Most people listen to their headphones at a level about 15 to 30 dB louder than the sound level they are experiencing. So, if noise-cancelling headphones were able to bring the workplace noise level down to a safe level of 85 dB, listening to music would then put the sound level back up to the 100 to 115 range.
Earbuds and Headphones are not Hearing Protection
There are several reasons to prohibit the use of earbuds and headphones as a substitute for hearing protection. They are not tested and certified as hearing protection. While they provide some noise reduction, we don’t know how much, and so cannot determine whether it is enough. And finally, if they are used to listen to music while working, the sound level will likely be high enough to negate most of the noise reduction they provide.
Don’t “Just Say No”
The next time the question comes up about wearing earbuds and headphones as a form of hearing protection, it is appropriate to say “no.” But don’t leave it at that if challenged. There are good reasons, and it is easier for personnel to comply with PPE requirements if they understand why they are in place. If they lose their hearing, they won’t be getting it back.
