Introduction
 Hearing
Protection Devices (HPDs) must be made available to all employees
exposed to an eight-hour Time-Weighted Average (TWA) of 85 dBA
or greater. The OSHA standard does not require
employers to enforce the wearing of HPDs unless the eight-hour
TWA exceeds 90 dBA (where exposure levels below 90 dBA have
not been incorporated into the noise dose), or an employee
exposed above an 8-hour TWA of 85 dBA has not received a baseline
audiogram, or experiences a Standard Threshold Shift (STS).
Since there is a significant risk of noise-induced hearing
loss at exposures of 85 dBA and above, the use of HPDs should
be enforced for all persons included in the audiometric testing
program.
 Top
Types of HPDs
 |
Earplugs are the most popular type of hearing protection devices. These are inserted into the ear canal to provide a seal against the canal walls. Preformed earplugs are made of flexible, vinyl materials and come in different sizes for different sizes of ear canals. Formable earplugs are made of materials that can be manipulated to conform to the shape of the wearer's ear canals. |
|
 |
Earmuffs enclose the entire external ears inside rigid cups. The inside of the cup is lined with acoustic foam, and the cup perimeter is fitted with a cushion that seals against the head around the ear by the force of a headband. |
|
 |
Semi-Aurals or Canal Caps are small stoppers which seal the entrance of the ear canal by the force of a band worn under the chin or behind the neck. They generally provide less protection than earplugs or earmuffs, and they are less comfortable for long-term use. Therefore, they are most suitable for brief periods of use,
not all day. |
Top
Hearing Protection Attenuation
All hearing protectors attenuate noise by creating a barrier to reduce the air-conducted sound reaching the eardrum. The level of protection achieved depends mainly upon the degree to which the protector achieves a seal. When the HPD does not fit properly (wrong size or design for the individual) or is not used correctly (due to inadequate training or carelessness), the wearer may not have an adequate seal.
HPD attenuation, or the ability of a particular protector to reduce the sound pressure levels for the specific noise environment where the protector is used, must be evaluated. Hearing protectors are required to attenuate down to 90 dBA-TWA unless an individual has experienced an STS. In this case, the hearing protectors must attenuate down to 85 dBA-TWA.
OSHA also requires that the adequacy of HPD attenuation be reevaluated whenever employee noise exposures increase to determine if the devices still provide adequate protection. The employer must then provide more effective hearing protectors where necessary.
Top
Attenuation Formula
The attenuation evaluation many employers use is the NRR (Noise Reduction Rating) method described in Appendix B of the noise standard. The NRR, shown on the label of the HPD package, is intended to give a rating of the protectors attenuation across a range of frequencies obtained from testing in a laboratory environment. The sound pressure level inside the HPDs is calculated, as follows, from the employee's A-weighted TWA:
TWA exposure - (NRR-7dB) = TWA protected The protected, or attenuated TWA should be below 85 dBA.
Top
"Real World" Attenuation
The problems with relying on the above method are:
- The TWA exposure is not known with great certainty; and,
- The NRR is a laboratory determined value.
Although employers are obligated to use one of the methods
described in Appendix B, this should not be relied upon to
protect the worker beyond a certain point. The "Real
World" protection factor may be as low as one-half
the NRR. This does not really pose a serious problem
because (1) the average, industrial HPD has a NRR of 22 dB
and (2) 92% of industrial noise exposures represent eight
hour equivalents of 95 dBA or less. Thus, 10 dB
protection is often all that is needed to reduce these exposures
to acceptable levels. Where TWAs exceed 95 dBA, much
more careful consideration should be given, rather than simply
relying on the NRR calculation. The protected TWA should
always be below 85 dBA regardless of the attenuation method
used.
Top
Training and Fitting HPD Users
Training must be provided in the use and care of hearing protectors. The OSHA standard requires that employees be given an opportunity to select their hearing protectors from a variety of suitable HPDs, and that the HPDs be provided at no cost to the employee. "Suitable" means that the HPD attenuates the noise adequately and can be worn by the particular employee. This selection process should help ensure that an HPD comfortable for the employee is selected. Add to that the feeling of participation or control in the selection process, and wearers are more likely to accept the requirement of wearing an HPD.
Employees must obtain a proper initial fit. Most audiometric testing firms will assist in the fitting. Initial fitting should include an anatomical check of the ear canal and ear drum by a qualified individual before insert-type HPDs are issued. Excessive amounts of cerumen (ear wax) may become compacted by plugs, and incorrectly fitted plugs can lead to outer ear inflammation. Too small a plug will not provide adequate attenuation.
For the construction industry, OSHA standard 1926.101 (b) requires all insert hearing protectors to be fitted individually to each overexposed employee by a competent person. A competent person is defined as a person trained in ear protection fitting and one who is able to recognize the difference between a good fit and a poor fit.
Top
Overcoming Employee Resistance
Like many other forms of personal protective equipment, some employees will resist the wearing or the correct wearing of HPDs, especially since there is no obvious threat to life or limb. If the HPD is not properly fitted, resistance to wearing can be expected. If an employee has a medical
problem with the ear aggravated by an HPD, resistance to wearing can be expected.
Probably the most common complaint (objection) is "I can't wear ear protection because I have to hear my machine". An employee may believe they must detect subtle changes in the machine/equipment's pitch or volume to implement proper control The question to be asked is "Is the complaint valid, or merely an objection to wearing of an HPD"? Often, the latter is the case. It must be understood that HPDs still allow sufficient noise energy to reach the ear so as not to interfere with the detection of machine operation. Chances are, the pitch or volume changes are not nearly as subtle as being claimed, and can still be detected with HPDs being worn.
However, if an employee is already suffering from a disabling hearing loss, the complaint could be legitimate. Such persons are particularly handicapped when it comes to hearing and understanding speech when wearing HPDs because the attenuated sound levels are too low (quiet) to stimulate their damaged hearing. These problems must be anticipated to be dealt with properly.
The failure to wear HPDs, regardless of the objections, will
result in additional hearing loss. This cannot be traded
off for the need to hear a particular change in an operation
generating hazardous noise levels. Where such audible
cues are critical to safety and production, consideration
needs to be given to who operates the machine and if audible
cues can be translated to visual cues.
Top
Enforcing The Use of HPDs
The ultimate success or failure of any hearing conservation program depends on the extent of management's commitment to impress upon the employees the necessity for personal hearing protection and to enforce its use. A conscientiously administered Hearing Conservation Program, including annual audiometric evaluations and mandatory use of personal hearing protection as a condition of employment, can minimize the effects of excessive noise exposure and eliminate any increased risk of impairment.
Proper use of HPDs should be supervised. HPDs need to be checked throughout the day for proper wearing. Common errors to check for are:
- Earplugs inserted improperly or not all the way;
- Earmuffs worn over glasses or hair; or,
- Earmuff bands worn behind the head.
Top
Maintaining HPDs
All types of HPDs need maintenance and cleaning, except disposable
plugs. Insert type plugs need to be washed daily to
keep them disinfected. Earmuff sealing pads are subject
to cracking from age and accumulation of sweat and skin oil
must be cleaned daily. They should be stored in cases
or safe places to prevent damage, inspected for signs of wear
and tear, and replaced when deterioration occurs.
Top
Posting Warning Signs
Warning signs should be posted accordingly, reminding employees to wear their HPDs while in areas where noise levels exceed 85 dBA.
Top
|
