Introduction
An estimated 14 million workers in the United States are exposed to hazardous noise. Noise, or unwanted sound, is considered one of the most pervasive occupational health problems. Prolonged exposure to excessive noise levels can produced "Noise-Induced Hearing Loss (NIHL)". During the course of a noisy day, sensitive cells in the inner ear (cochlea) become fatigued, causing workers to experience a temporary reduction in hearing sensitivity known as a Temporary Threshold Shift (TTS). If this pattern of daily TTS is repeated over a period of months or years, the result is a Permanent Threshold Shift (PTS), or reduced hearing ability. This gradual loss of hearing is the result of damage to the sensory cells in the inner ear and is not reversible by any medical treatment.
From studies of hearing loss, the National Institute for Occupational Safety and Health (NIOSH) estimated that from prolonged exposure to 90 dBA (decibels - A-weighted), about 1 employee in 5 (20%) will develop disabling NIHL. At 100 dBA, nearly half of the employees exposed will develop NIHL. For exposures at 85 dBA, the population of employees at risk of developing disabling NIHL drops to approximately 1 in 11 (9%) employees. Unabated, the hearing loss can reach disabling levels and qualify for hearing loss compensation in most states.
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What is a Hearing Conservation Program (HCP)?
In order to reduce the likelihood of NIHL, an effective hearing conservation program (HCP) is needed for all employees exposed to daily average sound levels of 85 dBA and above. The primary benefit of a hearing conservation program is that it prevents occupational hearing loss and the resulting disability. Other benefits include improved quality of production through more effective communication, reduced accident rates, reduced stress and fatigue related to noise exposure, and increased work efficiency. The bottom line is that hearing loss from any cause reduces the quality of life for the affected individual and increases costs for the employer. Any effective HCP benefits both employers and employees.
The basic elements of an effective hearing conservation program include:
- Initial Noise Monitoring. Initial
monitoring identifies noise sources and the employees who
are exposed at or above 85 dB(A), time-weighted average
(TWA).
- Engineering and Administrative Controls. Engineering
controls are the desired method to reduce the noise coming
off the source(s) to acceptable levels. Engineering
controls can involve substantial start-up costs, or unavailable
technology. In these and other cases, engineering
controls may not be deemed feasible. Administrative
controls, such as job rotation and work practices, can be
used to reduce the duration of exposure to noise to keep
daily noise exposures below 85 dBA. Administrative
controls present other feasibility problems that may prevent
their implementation.
- Audiometric Testing program. Audiometric
testing is used to establish baselines and monitor the hearing
ability of overexposed employees.
- Hearing Protection Devices (HPDs). Ear
plugs, earmuffs, and other hearing protectors are used to
attenuate the noise reaching the employee's ears.
- Employee Training. A training program
is needed to encourage the wearing and proper use and care
of HPDs.
- Recordkeeping. Exposure monitoring,
audiometric testing, and training records need to be maintained.
- Periodic Noise Monitoring. To ensure
proper identification of overexposed employees following
significant changes in equipment, operations, processes
or machinery that will affect the exposed group, periodic
monitoring is needed.
Does hearing conservation really work? A recent study looked at the results of over 588,000 audiometric tests conducted over a five year period. The purpose of the study was to determine if enforcement of the hearing conservation amendment has been effective at reducing the incidence of noise induced hearing loss. The results indicate that there was a significant annual decrease in the number of employees with standard threshold shifts (from 4.7% to 1.2%) and permanent threshold shifts (from 2.5% to 0.5%), where hearing conservation programs have been implemented and maintained according to the OSHA standard. The data collected during this five year study clearly supports the notion that by aggressively adhering to and enforcing the hearing conservation policies proposed by OSHA, the incidence of noise-induced hearing loss can be reduced and effectively controlled.
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Becoming Familiar with Noise Standards
The Occupational Safety and Health Administration (OSHA) regulates exposure to noise in the work place under 29 CFR 1910.95 (General Industry) and 29 CFR 1926.52 (Construction). These standards require employers to 1) limit workers' exposures to noise below a specified limit for 8-hour average exposures, and 2) implement a hearing conservation program for employees exposed above specified limits to reduce the likelihood of noise-induced hearing loss from employees being exposed over their entire working lifetimes.
The Permissible Exposure Limits (PELs) are enforcement criteria used by OSHA in determining when a violation of the Occupational Safety and Health Act has occurred. The current PEL for noise, established in 1971, is based on the sound pressure level (measured in A-weighted decibels - dBA) and the duration of exposure. The following table is included in both the general industry and construction standards. Protection against the effects of noise exposure are required when sound levels exceed those shown below.
| Permissible Noise Exposure |
| Duration per day, hours |
Sound level, dBA slow response |
| 8 |
90 |
| 6 |
92 |
| 4 |
95 |
| 3 |
97 |
| 2 |
100 |
| 1 1/2 |
102 |
| 1 |
105 |
| 1/2 |
110 |
| 1/4 or less |
115 |
Therefore, for both general industry and construction, the
PEL is 90 dBA as a daily 8-hour average. The following
outlines the differences between the OSHA General Industry
and Construction standards.
General Industry. Since 1971, it has been recognized by OSHA that a significant portion of the population is at risk of disabling hearing loss at exposures below 90 dBA for 8-hours. In 1981, the noise standard for general industry was amended to include an 8-hour average of 85 dBA as the Action Level. The Action Level was included in the Hearing Conservation Amendment, requiring hearing conservation programs for all employees whose noise
exposures equal or exceed an 8-hour time-weighted average of 85 dBA.
Construction The construction standard (29 CFR 1926.52) requires that feasible administrative or engineering controls and a continuing, effective hearing conservation program be implemented in all cases where noise exposures exceed 90 dBA. At the time the general industry standard was updated to include an Action Level of 85 dBA, the construction standard was not updated. However, the risk is the same for employees, regardless of where they are exposed.
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Scope of This Program Kit
Since the risk of hearing loss for employees is significant
at levels below 90 dBA, this compliance kit will not make
distinctions between engineering, administrative controls,
or other hearing conservation program elements required at
85 dBA or 90 dBA. Since the goal is to prevent the progression
of occupational hearing loss in the most cost effective manner,
all hearing conservation program elements (including engineering
controls) are necessary to control NIHL. These program
elements should be instituted for all employees exposed at
or above 85 dBA as an 8-hour time-weighted average.
Although OSHA and most states have required employers to have a hearing conservation program (HCP) for noise exposed employees since 1971, many companies have not developed a program, or in some cases, have only implemented partial programs. To ensure that a HCP accomplishes its purpose, the prevention of noise-induced hearing loss, all the necessary elements must be in place. The purpose of this guide is to assist employers in developing and implementing effective hearing conservation programs
in their operations.
The OSHA regulations specify minimum requirements for employers to meet. The standard provisions have been outlined here to assist you in comparing the elements of your program to the OSHA standards for compliance purposes. In this kit, additional or modified program elements have been included to ensure hearing conservation programs effectively accomplish what they are designed to do -- prevent occupational hearing loss.
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Identifying Responsible Staff
Hearing conservation should be a continuing program in your facility. This is not a "one shot deal". In order to have a successful program, responsibility must be assigned for both the initial and ongoing activities. In some cases, these activities may already be part of current job assignments. For example, site supervisors are frequently responsible for on-the-job training sessions. Early identification of the
responsible employees, and involvement of them in developing your plan of action, will result in a more effective program design. Evaluating the effectiveness of your program will also be enhanced by involvement of affected employees.
For any safety and health program, success depends on commitment at every level of the organization. This is particularly true for hearing conservation, where success often requires change in behavior. This will only occur if employees understand the program, and are committed to its success, and if employees are motivated by the people presenting the information to them.
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Identifying Employees to be Included in the Hearing Conservation Program
Initial noise monitoring is necessary to identify those employees who are exposed to noise at or above 85 dBA averaged over 8 working hours, or a noise dose of 50%. The noise exposure measurements taken to make this determination must include all continuous, intermittent, and impulsive noise within an 80 dB to 130 dB range and must be taken during a typical work situation. All sound survey equipment must meet ANSI Type 2 accuracy requirements, and must be properly calibrated before and after each survey.
The most commonly used equipment for evaluating employee noise exposures are sound level meters and audio dosimeters. Sound level meters are used to measure sound pressure (noise) levels and with proper use, can be used to calculate the employee's noise dose. The results of sound pressure level measurements can also be used to compile a "noise map" of the facility for assistance in implementing administrative controls such as job rotation. Audio dosimeters are essentially sound level meters worn by employees. These devices integrate the wide range of sound pressure levels typically encountered by employees as they move around the work area. The resulting measurement is the employee's noise dose, which can be converted into the equivalent sound pressure level to compare to the OSHA Action Level of 85 dBA.
Equipment capabilities and types of monitoring are two important considerations when developing a sampling strategy for evaluating noise exposures. Complex noise patterns, such as those encountered by a highly mobile employee can not be accurately evaluated with a hand-held sound level meter, and thus, an audio dosimeter should be used. Personal monitoring (readings taken with the microphone in the worker's hearing zone) is necessary to evaluate employee exposures. Area monitoring may be conducted to establish the noise "profiles" of a particular room or area. The type of noise monitoring and equipment used should be selected according to the desired survey results. Noise monitoring should be repeated when changes in production, processes, or controls increase noise exposures. Such changes may mean that additional employees need to be included in the program. You may also want to monitor after changes appear to reduce noise exposures (e.g., after replacing the older machine with a newer, quieter model). The monitoring may show that employees no longer need to be included in a Hearing Conservation Program.
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Preparing and Implementing a Hearing Conservation Program
All workplaces where employees are exposed to noise above the OSHA Action Level of 85 dBA for 8-hour average exposures should have a written plan which describes how the standard will be implemented in that facility. Preparation of a plan is not just a paper exercise - all of the elements must be implemented in the workplace in order for the program to be effective.
The plan does not have to be lengthy or complicated. It is intended to be a blueprint for implementation of the program - an assurance that all aspects of
the requirements have been addressed.
This kit provides a "generic" example of a written program. Although such general guidance may be helpful, you must remember that the written program has to reflect what you are doing in your workplace. Therefore, if you use a generic program, it must be adapted to address the facility it covers. For
example, the written plan must list the affected employees or areas at your site, indicate who is responsible for the various aspects of the program in your facility, and indicate how any written materials or exposure records will be made available to employees.
If OSHA inspects your workplace and suspects a noise problem in your facility or on your work site, the OSHA compliance officer will ask to see your exposure monitoring results and written plan at the outset of the inspection. Many of the items listed here will be considered when evaluating the effectiveness of your program.
The written Hearing Conservation Program should describe the engineering and administrative controls used at your facility, audiometric testing program in place to evaluate the effectiveness of any controls, hearing protection devices provided to the employees and the method of selection, training procedures, and recordkeeping practices. The following discussion provides descriptions of the program elements necessary for an effective hearing conservation program.
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Engineering Controls
Engineering controls should be used wherever it is economically and technically feasible to lower the noise exposure of workers. Such controls include:
- Enclosures. Full or partial enclosure
of machines using materials which absorb and reflect noise
energy. An alternative is to enclose the employee.
- Barriers. A form of partial enclosure
with reflective and/or absorptive characteristics to block
the flow of noise energy past a given point.
- Damping. The practice of reducing
the vibration of machine parts by stiffening or affixing
damping materials
- Vibration Isolation. To reduce the
transmission of vibration and its subsequent noise generation
through the use of isolating springs and elastomeric materials
at transmission points.
- Silencers and Mufflers. To attenuate
the noise of rapidly escaping air.
- Room Treatments. Highly reflective
floors, walls and ceilings add to the noise dose through
reflected noise. Treating these surfaces with absorbing
materials results in a reduction of the reflected noise.
Engineering controls include a number of simple to complex treatments to consider. Simple treatments, such as barriers, vibration isolation, and damping may be obtained through a noise supplier. However, complex treatments such as enclosures and room absorption require careful material selection based on analysis of the frequencies of the noise present through octave band analysis, and detailed construction parameters. Complex treatments should be designed by an acoustical engineer.
Although engineering controls usually involve higher initial costs,
successful implementation and reduction of employee exposures below 85 dBA negate the need for continual audiometric testing and hearing protective device programs. The maintenance of engineering controls must be regularly scheduled to ensure their continued effectiveness.
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Administrative Controls
Typically, administrative controls involve some degree of job rotation or cessation of activity in areas that would otherwise result in overexposure after one-half of the permissible duration has been reached. The goal is to reduce the TWA to below 85 dBA or the daily noise dose to below 50%. Thus, a noisy job that generates 90 dBA is administratively controlled if workers are
exposed for less than four hours and work in "quiet" (<80 dBA) areas the rest of the day. If the job must be done for eight hours, then workers must be rotated to quiet areas that will not result in additional noise dose. The challenges with implementing administrative controls are:
- Not having any quiet areas (less than 80 dBA) where noise
dose will not accumulate.
- Cross training of workers to perform all tasks they are
rotated to; or,
- Labor agreements restricting the movement of employees
between departments or job classifications.
However, where these problems can be overcome, administrative controls are an effective means of noise control. Accurate recordkeeping of work patterns, training employees in the importance of maintaining established time limits, as well as accurate noise survey information on which the work patterns will be based, are all important for a successful program. If the daily noise doses can be reduced to below 50%, audiometric testing programs and use of hearing protection devices are not required.
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Audiometric Testing Program
All employees exposed at or above 85 dBA-TWA (50% Noise Dose), whose exposure will not be reduced by engineering or administrative controls, must be included in an audiometric testing program. Audiometric testing not only monitors the sharpness or acuity of an employee's hearing over time, but also provides an opportunity for employers to educate employees about their hearing and the need to protect it.
A licensed or certified audiologist (specialist dealing with
individuals having impaired hearing), an otolaryngologist
(physician specializing in the diagnosis and treatment of
disorders of the ear, nose, and throat), or a physician must
be responsible for the program. Both professionals and
trained technicians may conduct audiometric testing.
The professional in charge of the program does not have to
be present when a qualified technician is conducting testing,
however. The professional's responsibilities include
overseeing the program and the work of the technicians, reviewing
problem audiograms, and determining whether referral to a
physician is necessary.
The important elements of an audiometric testing program include baseline audiograms, annual audiograms, training, and follow-up procedures. Exit, or termination, audiograms are also recommended to document hearing thresholds. The audiometric testing program should indicate whether hearing loss is being prevented by the hearing conservation program.
Baseline Audiograms
The baseline audiogram is performed at the time of or as soon after employment as possible. The baseline will be used as a reference against which all future audiograms will be compared. If hearing protection devices are effective and being worn properly, an employee's hearing should not deviate from the baseline, except for the gradual loss from presbycusis (hearing loss due to aging) or medical problems not related to noise-induced hearing loss.
The OSHA standard allows up to six months after an employee's initial exposure before baselines must be established. Under OSHA's "mobile testing van exception", a new employee's baseline does not have to be established for one year. However, by obtaining baseline audiograms as soon as possible after employment, any preexisting hearing loss can be documented. This allows for a more accurate determination of any change in the employees' hearing resulting from noise exposure in your workplace. Therefore, baseline audiograms should be obtained for all employees as soon as possible after assignment to an area where exposures exceed the OSHA Action Level. Many states allow employers to "deduct" any pre-employment hearing loss an employee has, as long as that loss is documented within the time specified by the state.
Annual Audiograms
At least annually after the baseline audiogram, a new audiogram must be obtained. The purpose of this audiogram is to monitor the effectiveness of the hearing protection devices. If no significant deviation of the baseline threshold has occurred, then the hearing conservation measures are considered effective. It is important to test hearing on an annual basis
to identify deterioration in hearing ability so that protective follow-up measures can be initiated before hearing loss progresses.
The annual audiograms must be routinely compared to determine whether the audiogram is valid, and to determine whether the employee has lost hearing ability -- i.e., if a Standard Threshold Shift (STS) has occurred. STS, as defined by OSHA, is an average shift in either ear of 10 dB or more at 2000, 3000, and 4000 Hertz. Action is required when shifts reach or exceed this specified point. Employees should be notified within 21 days from the time the determination is made that their audiometric test results showed an STS. Some employees may need to be referred for further testing if the professional determines that their test results are questionable, or if they have an ear problem of a medical nature that is thought to be caused or aggravated by wearing hearing protection.
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Hearing Protection Devices
Use
Hearing protection devices (HPDs) should be made available to all employees exposed to an eight hour TWA of 85 dBA or greater. Enforcement of the wearing of HPDs is not required by OSHA unless the eight hour TWA exceeds 90 dBA, except when (1) an employee has suffered a Standard Threshold
Shift, or (2) an employee is waiting longer than six months for the baseline audiogram to be performed. In these two cases, enforcement of wearing HPDs is mandatory at 85 dBA-TWA and above. In this compliance kit, enforcement of HPD use is recommended at exposures of 85 dBA and above, mainly because the risk of hearing loss is significant at 85 dBA.
Choosing and Evaluating HPDs
Employees should be given an opportunity to select their hearing protectors from a variety of suitable protectors. Suitable means that the HPD attenuates the noise adequately and can be worn by the particular employee. Attenuation is the ability of a particular protector to reduce the sound pressure level for the specific noise environment in which the protector will be used. Using the results of personal noise monitoring, hearing protectors should be selected which attenuate the occupational noise exposures to below 85 dBA. Hearing protection devices are assigned a laboratory determined value called a Noise Reduction Rating
(NRR). An attenuation formula is then used to determine the NRR needed based on the employee's TWA exposure to noise. Attenuation formulas are included in Appendix B of 1910.95.
The laboratory-based attenuation (NRR) for hearing protectors
is rarely achieved in the workplace. Since an employee's
daily TWA exposure is not known with great certainty, and
NRRs are laboratory-determined values, "real world"
protection factors may be as low as one-half of the NRR.
This may not pose a serious problem since the average industrial
HPD has an NRR of 22 dBA and most industrial noise exposures
are 95 dBA or less. However, where employee exposures
exceed 95 dBA, more careful consideration should be given
to HPD selection than just relying on the NRR calculations.
Training in the use and care of hearing protectors should be provided. The selection process should help ensure that an HPD comfortable for the employee is selected. Proper initial fitting is vital to ensuring the effectiveness of HPDs. Most audiometric testing firms will assist in the fitting. In addition, employees should be supervised on the job to ensure HPDs are worn correctly once selected and fitted.
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Training Program
A training program is needed for all employees exposed at or above the Action Level. The training program should be repeated annually for these employees. New employees should receive the training as part of their indoctrination. When workers understand the reasons for the hearing
conservation program's requirements and the need to protect their hearing, they will be better motivated to participate actively in the program and to cooperate by wearing their protectors and taking audiometric tests.
The training program should include the following information:
- The effects of noise on hearing;
- The purpose of hearing protectors, the advantages, disadvantages
and attenuation of various types, and instructions on selection,
fitting, use, and care; and,
- The purpose of audiometric testing and an explanation
of the test procedures.
The training program may be structured in any format, with different portions conducted by different individuals at different times, as long as the required topics are covered. All of these topics are included in various audiovisual libraries available commercially or through safety libraries.
OSHA's Hearing Conservation standard does not require employers to maintain records of employee training, but many employers choose to do so. This may help in monitoring the program to ensure that all employees are appropriately trained. If a training program is already in place, you may only need to supplement it with information about the company's Hearing Conservation program. For example, construction employees that are already in compliance with OSHA's construction training standard will have little extra training to do.
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Recordkeeping
The recordkeeping requirements of OSHA 1910.95 are straightforward. Noise exposure measurement records must be kept for 2 years. Records of audiometric test results must be maintained for the duration of employment of the affected employees. However, audiometric test records should be retained for terminated employees at least until the statutory deadline for filing a claim has passed. Audiometric test records must include:
- The name and job classification of the employee;
- Date;
- Examiner's name;
- Date of the last acoustic or exhaustive calibration;
- Measurements of the background sound pressure levels in audiometric test rooms; and,
- The employee's most recent noise exposure measurement.
Noise survey information and results, hearing protectors and training, and records of employee notifications should be maintained to properly document the steps taken to effectively protect employees from noise-induced hearing loss.
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Periodic Noise Monitoring
The role of the initial monitoring was to identify those employees or groups of employees who need to be included in the hearing conservation program, and to establish a "noise map" of the area. The main purpose of periodic monitoring is to evaluate the effect of process, equipment and other changes on the exposed group of employees.
Periodic monitoring is triggered when a significant change in the process, machinery, or controls would change the exposure. For example, retooling an assembly line from pneumatic to electric screw guns may reduce average noise levels to below 85 dBA, exempting the area from further hearing conservation measures. Conversely, increasing the amount of machinery in a given area without increasing available space, may overexpose a group of employees formerly exposed below the Action Level.
After installing engineering or administrative controls, remonitoring should be done to ensure that the controls are reducing exposures to acceptable levels. If changes in the process are such that new average noise levels may exceed the attenuation capabilities of the HPDs in use, remonitoring may have to be conducted to select new HPDs.
If your hearing conservation program adequately addresses the means of protecting employees against the effects of excessive exposure to noise, it will be found to be in compliance with the Hearing Conservation Standard, and effectively prevent occupational hearing loss.
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