Using Hearing Protectors

Hearing protectors are protective equipment used to help prevent hearing loss due to sudden or chronic exposure to loud noises.

Description:

Hearing protectors - ear plugs, canal caps and ear muffs - protect the user from hearing loss due to chronic exposure to loud noises. Engineering and administratrive controls should be used to maintain an average workplace noise level below 90 dB and if possible below 85 dB. Worker noise exposure must be known or estimated. If average noise levels after using engineering and administrative controls exceed 90 dB(A), hearing protectors must be used. Hearing protectors should be used if the average noise level exceeds 85dB(A).  Hearing protectors should be selected with consideration of both the noise exposure and the conditions on the job. 

Hearing protectors typically provide much less protection in the field than they do in the laboratory tests used to establish the noise reduction rating (NRR) that EPA requires to appear on their packaging. OSHA recommends that the NRR be "derated" by subtracting 7 dB from the label vaulue and dividing the remainder in two.  A hearing protector with an NRR of 25 under this formula would be derated to a protection level of (25db-7db)/2 or 9 dB.

It is critical that hearing protectors be properly inserted and worn, otherwise they may provide little or no protection.  Follow the manufacturer's direction carefully. For foam and premolded plugs and canal caps, the outer ear should be pulled out and back with the opposite hand to straighten the ear canal. Foam plugs should be rolled down tightly with no creases, inserted fully and held for a few seconds while they expand. Premolded plugs  should be fully inserted. Muffs should be placed snuggly around the ears with nothing disrupting their tight fit with the skin.

Guides to hearing protector use are available from NIOSH and E.A.R.

Try to reduce the amount of noise in your workplace
The danger of hearing loss is reduced by lowering the total amount of noise entering your ears. First, try to reduce your workplace noise exposure by using quieter tools, by keeping noisy operations as far away from you as possible, or by placing a barrier between you and the noise source. If you still need to shout to be heard at arms length, you need to use hearing protectors.
Know or estimate your noise exposure
Noise levels are reported using a logarithic– not linear- scale with units called decibels (dB).  Workplace noise is usually measured with an instrument called a sound level meter (SLM) that is set to a filtered scale  (the A scale) that weights different noise frequencies to match their impact on hearing. Those results are reported in levels of dB(A). Each 3 dB change in noise level indicates a doubling or halving of the noise level. A 10 dB change indicates a 10 fold difference and a 20 dB change indicates a 100 fold difference. The human ear is not very good at detecting changes in sound level. If a noise level increases from 80dB to 110 dB most people will only hear about an 8 fold increase in sound level even though the true energy (and risk) difference is 1000 fold! Small changes in db levels are important! Reducing the noise to your ears by 5 dB or less can make a big difference in your chances of retaining your hearing.
You can find out how much noise you are exposed to by having a qualified person use a SLM to measure the noise level as you perform each of your work tasks. You can also wear a noise dosimeter for a full shift or a representative part of a shift to get a measure of your total noise exposure. Either result should be interpreted by a qualified person. If you have not had your work noise level monitored you can refer to lists like those below that show typical construction tasks and the ranges of noise levels you can expect when doing or around those doing those tasks.
You should keep the average noise level below 90 dB or, if possible, below 85 dB. You can use a higher level of protection than required, but too much overprotection when you are exposed to traffic, overhead loads or other hazards may make it difficult to hear warning noises.
For very loud tasks, such as chipping inside a cement truck or grinding inside a boiler, hearing protection may not provide adequate protection for the typical worker to do that task for a full 8 hour shift. Double protection – plugs and muffs – should be used for this level of noise and work should be limited to no more than one hour of work per day at that level.

Masonry Tasks, in order of increasing average noise level 

 

Tasks Average Noise Level (dBA) Maximum Noise Level (dBA)
Break, Rest, Lunch 84.8 103.0
Operating Forklift 88.5 110.9
Manual Material Handling 89.4 105.3
Bricking, Blocking, Tiling 91.6 114.0
Grouting and Mortaring 92.9 113.7
Pointing, Cleaning, Caulking 95.3 115.2
"Other" Tasks 96.4 114.7
Operating Work Vehicle 98.0 116.7

 

Masonry Tools, in order of increasing average noise level 

 

Tools Average Noise Level (dBA) Maximum Noise Level (dBA)
Powder Actuated Tool 82.6 111.0
Welding & Cutting Equipment 87.1 108.5
No Tool 89.7 108.5
Hammer, Mallet, Sledge 90.4 115.4
Screw Gun, Drill Motor 91.7 115.8
"Other" Tools 92.8 111.4
Other Hand Power Tools 95.4 118.3
Rotohammer 96.3 120.0
Hand Power Saw 97.2 114.0
Stationary Power Tool 101.8 119.8

 

Select hearing protectors to match your noise exposure

Hearing protectors have an EPA Noise Reduction Rating (NRR) that represents the noise reduction achieved under laboratory conditions. These reductions are seldom achieved in the field so OSHA recommends that NRRs be “derated”. OSHA recommends subtracting 7 dB from the NRR and then dividing that number by 2. Following OSHA’s recommendation a foam ear plug with an NRR of 33 could be relied on to provide a true reduction of 13 dB for a typical user if inserted following the manufacturer’s instructions. If both ear plugs and muffs are used, 5 dB of protection is added to the protection of the best rated protector. Higher levels of protection can be achieved if hearing protectors are carefully fitted by a qualified person and inserted by very well trained users.

 

Protector NRR Derated NRR Range of Use Ear Noise Level
  dB dB dB(A) dB(A)
Canal Caps 17-21 5-7 90-97 85-90
Ear Plugs 23-33 8-13 90-103 82-90
Ear Muffs 27-37 10-15 90-105 80-90
Plugs + Muffs +5 dB 15-20 100-110 85-90

 

*NIOSH recommends allowing more protection for muffs (70% of NRR-7dB) and less for pre-molded plugs (30% of NRR-7 dB)

**assumes that the highest rated protector in each group is used at the highest noise level

Reduce exposure times for very high noise levels

Allowable noise exposure levels are determined for a person working an 8 hour day. If the selected hearing protection does not reduce the noise level in the ear to below 90 dB, the amount of time of noise exposure must be reduced. A reduction of 3 db of noise is allowed for each cutting of exposure time in half.   Tasks such as chipping concrete  inside a mixer or grinding inside a boiler expose a worker to constant noise levels of 105 dB or more. A worker doing these or other task at noise levels above120 dB(A) should use double protection and their time doing that task should be limited one hour or less per day of exposure at that level.  Greater time at task may be allowed if both the noise level and hearing protection use are monitoring by a qualified person and the expected noise exposure level does not exceed 90 dB(A)

Wearing Hearing protectors
An ear plug that is not properly inserted or is worn incorrecty may provide little or no protection!  NIOSH provides the following guideline for using hearing protectors.
Fitting pre-molded plugs and canal caps
1.       Reach over the top of the head and pull up and back on the top of the ear. This straightens out the ear canal so that the plug can go in far enough.
2.       Insert the plug fully into the straightened ear canal.
3.       Gently pull out on the plug. If you feel pressure inside the ear you have a good seal. Do not pull hard enough to unseal the plug!
Fitting foam ear plugs
Some formable foam ear plugs come in different sizes. If the size that you are using cannot be fitted comfortably into your ear canal, or you cannot get a snug fit, try a different size.
Foam plugs should be inserted with clean hands to the extent possible.
1.       Roll the formable plug between your thumb and forefinger to compress it into a small, smooth round cylinder.
2.       Reach over the top of the head and pull up and back on the top of the ear. This straightens out the ear canal so that the plug can go in far enough.
3.       Insert the tightly rolled plug into the straightened ear canal.
4.       Insert the plug fully and hold it in place for a few seconds into it expands and seats itself in the ear canal.
5.    To check your fit, cup your hands over your ears and make a good seal. Count out loud while slowly cupping and uncupping your ears. If you have a good fit, your voice should sound about the same.
 
 

Earplugs (non-foam) from 3M (Photo courtesy of 3M)

Fitting ear muffs
 Muffs must fully enclose the ears to seal against the head
1.       Adjust the headband so cushions exert even pressure around the ears.
2.       Pull hair back and out from beneath the cushions.
3.       Don’t store pencils or wear caps under the cushions.
Keep your hearing protectors clean.
Ear plugs can be washed in mild liquid detergent and warm water. Squeeze excess water from the plug and air dry. Discard any plug that has lost its firmness, is torn, cracked or otherwise deformed or does not re-expand its original size. Store plugs in a carrying case. 

Risks Addressed:

Loss of hearing due to chronic and acute noise exposure

How Risks are Reduced:

Hearing protectors reduce the amount of sound energy that enters the inner ear.

It is well established that hearing protectors can reduce the amount of noise entering the inner ear and that excessive chronic noise exposure causes hearing loss.  However, the research literature is less certain about the amount of noise reduction that  hearing protectors provide when worn in the field.  Both OSHA and NIOSH have recommended  significantly "derating" the noise reduction rating assigned to hearing protectors based upon EPA test criteria.  The agencies do not agree on the details of the derating scheme.

Effects on Productivity:

N/A

Additional Considerations:

Hearing protectors may also reduce work related stress by reducing irritating noises.

Warning devices and needed operations related sounds can usually be heard when moderate and lower rated hearing protectors are used.  Site traffic and material handling safety plans should take noise and hearing protection into consideration when establishing rules for vehicle and material movement and warning methods.  High level hearing protection should not be worn in high vehicle or material movement areas unless their use is clearly provided for in the site traffic and crane safety plans.

An annual hearing test should be conducted to determine if workers have had any loss of hearing ability.  Any significant shift in the worker's hearing ability should result in a reevaluation of the hearing conservation program including worker retraining in the use of protectors.