The surest method of preventing occupational deafness is to reduce noise at the source by engineering methods. However, in certain workplace conditions, there is very little or nothing one can do to reduce noise at the source. In such workplaces, workers wear hearing protectors to reduce the amount of noise reaching the ears.
People should wear a hearing protector if the noise or sound level at the workplace exceeds 85 decibels (A-weighted) or dB(A). Hearing protectors reduce the noise exposure level and the risk of hearing loss.
If hearing protection is required, then a complete hearing conservation program should be instituted. A hearing conservation program includes noise assessment, hearing protector selection, employee training and education, audiometric testing, maintenance, inspection, record keeping, and program evaluation.
The effectiveness of hearing protection is reduced greatly if the hearing protectors do not fit properly or if they are worn only part time during periods of noise exposure. To maintain their effectiveness, they should not be modified. Remember, radio headsets are not substitutes for hearing protectors and should not be worn where hearing protectors are required to protect against exposure to noise.
Select hearing protection that is:
Semi-insert ear plugs which consist of two ear plugs held over the ends of the ear canal by a rigid headband.
Ear muffs consist of sound-attenuating material and soft ear cushions that fit around the ear and hard outer cups. They are held together by a head band.
The choice of hearing protectors is a very personal one and depends on a number of factors including level of noise, comfort, and the suitability of the hearing protector for both the worker and his environment. Most importantly, the hearing protector should provide the desired noise reduction. It is best, where protectors must be used, to provide a choice of a number of different types to choose from.
If the noise exposure is intermittent, ear muffs are more desirable, since it may be inconvenient to remove and reinsert earplugs.
Manufacturers provide information about the noise reducing capability of a hearing protector as an NRR (noise reduction rating) number. The NRR ratings are based on noise reduction obtained in laboratory conditions.
NIOSH recommends using subject fit data based on ANSI S12.6-1997 [or most current edition] to estimate hearing protector noise attenuation.
If subject fit data are not available, NIOSH recommends derating hearing protectors by a factor that corresponds to the available real-world data. Specifically, NIOSH recommends that the labeled NRRs be derated as follows:
1. When the noise exposure level in dBC is known, the effective A-weighted noise level (ENL) is:
ENL [dB(A)] = Workplace noise level in dBC - derated NRR
2. When the noise exposure level in dB(A ) is known, the effective A-weighted noise level is:
ENL = Workplace noise level in dB(A) - (derated NRR -7)
There are other single number ratings available. For details refer to the Canadian Standard CSA Z94.2. Another single number rating is based on (Subject Fit) Real Ear Attenuation measurements, known as Single Number Rating (Subject Fit 84th percentile) and abbreviated as SNR (SF 84) (for details see ANSI Standard S12.6). "SF 84" indicates that 84% of the users in a well run hearing conservation program are expected to receive at least that much protection.
An SNR is a single number rating system determined according to International Standard ISO 4869. The tests are carried out by commercial laboratories that are independent of the manufacturers. Like NRRs, SNRs are expressed in dB's and are used as a guide for comparing the potential noise reduction capability of different hearing protection devices. Since the procedures for measuring NRRs and SNRs are different, the NRR and SNR values for an individual hearing protector are different. For further details please refer to the Canadian Standard CSA Z94.2 or American Standard ANSI S12.6.
There are advantages and disadvantages associated with the use of either ear muffs or ear plugs.
Ear plugs can be mass-produced or individually molded to fit the ear, and they can be reusable or disposable. On the positive side, they are simple to use, less expensive than muffs, and more comfortable in hot or damp work areas. On the negative side, they provide less protection than some muffs, and should not be used in areas having noise levels over 105 dB(A) (A-weighted decibels). They are not as visible as muffs and a supervisor cannot readily check to see if workers are wearing them. They must be properly inserted to provide adequate protection.
Ear muffs can vary with respect to the material and depth of the dome, and the force of the headband. The deeper and heavier the dome, the greater the low-frequency attenuation provided by the protector. The headband must fit tightly enough to maintain a proper seal, yet not be too tight for comfort. On the positive side, ear muffs can usually provide greater protection than plugs, although this is not always true. They are easier to fit, generally more durable than plugs, and they have replaceable parts. On the negative side, they are more expensive, and often less comfortable than plugs, especially in hot work areas. In areas where noise levels are very high, muffs and plugs can be worn together to give better protection.
The following table summarizes the differences between ear plugs and ear muffs.
|Comparison of Hearing Protection|
|Ear Plugs||Ear Muffs|
|Advantages: ||Advantages: |
|Disadvantages: ||Disadvantages: |
The human aspects of hearing protection are particularly important since the only useful kind of protection is the protection that is actually worn. Some people do not accept particular kinds of protectors; every human being is different, and the anatomy of the ear and ear canal can vary significantly from person to person.
It is a good idea for the employer to provide a number of different types of hearing protection from which workers can choose, keeping in mind any safety or hygienic reasons for not providing a particular kind of protector. That is, a particular type of protector should not be used if noise levels are too high or if it proves to be inadequate from a hygienic point of view. For example, ear plugs which are used in a plant setting where people reuse them throughout the day, often reinserting them with dirty fingers, can introduce dirt and bacteria into the ears, causing ear infections.
The bottom line on hearing protection is worker preference. If the workers do not like the type of protection (for example, if it is uncomfortable, does not fit well, or is impractical), they will not wear it.
Follow manufacturers' instructions. With ear plugs, for example, the ear should be pulled outward and upward with the opposite hand to enlarge and straighten the ear canal, and insert the plug with clean hands.
In order to get full benefit, hearing protectors must be worn all the time during noisy work. If hearing protectors are removed only for a short duration, the protection is substantially reduced. The following table gives a maximum protection provided for non-continuous use of an ideally fitted "100%" efficient hearing protector. For example if one takes off his/her hearing protector for 5 min in a 8-hour shift, the maximum protection will be 20 dB.
|Maximum protection provided by |
non-continuous use of Hearing Protection
|Percent time used||Maximum Protection|
Ear protectors must be used ALL THE TIME to get full benefit.
Document confirmed current on August 23, 2012
Document last updated on July 25, 2007