ENGINEERING AND ADMINISTRATIVE CONTROLS
Engineering and administrative controls are essential to achieve an effective hearing
loss prevention program. Engineering and administrative controls represent the first two
echelons in the NIOSH Hierarchy of Controls: 1) remove the hazard, 2) remove the worker.
The use of these controls should reduce hazardous exposure to the point where the risk to
hearing is eliminated or at least more manageable. Engineering controls are
technologically feasible for most noise sources but their economic feasibility must be
determined on a case-by-case basis. In some instances the application of a relatively
simple noise control solution reduces the hazard to the extent that the other elements of
the program, such as audiometric testing and the use of hearing protection devices, are no
longer necessary. In other cases, the noise reduction process may be more complex, and
must be accomplished in stages over a period of time. Even so, with each reduction of a
few decibels, the hazard to hearing is reduced, communication is improved, and
noise-related annoyance is reduced as well.
It is especially important that companies specify low noise levels when purchasing new
equipment. Many types of previously noisy equipment are now available in noise-controlled
versions, so a "buy quiet" purchase policy should not require new engineering
solutions in many cases.
A summary of OSHA's requirements for engineering and administrative controls can be
found in items no. 1-3 of Appendix A in this guidebook. Readers may obtain some practical
guidance in the section entitled "Engineering and Administrative Controls" of
For hearing loss prevention purposes, engineering controls are defined as any
modification or replacement of equipment, or related physical change at the noise source
or along the transmission path (with the exception of hearing protectors) that reduces the
noise level at the employee's ear.
Typical engineering controls involve:
1. Reducing noise at the source.
2. Interrupting the noise path.
3. Reducing reverberation.
4. Reducing structure-borne vibration.
Common examples of the implementation of such controls are:
1. Installing a muffler.
2. Erecting acoustical enclosures and barriers.
3. Installing sound absorbing material.
4. Installing vibration mounts and providing proper lubrication.
Assessing the applicability of engineering controls is a sophisticated process. First,
the noise problem must be thoroughly defined. This necessitates measuring the noise levels
and developing complete information on employee noise exposure and the need for noise
reduction. Next, an approach to engineering control must be developed, requiring the
identification of individual noise sources and an assessment of their contributions to the
overall noise levels. Once identified and analyzed, the above controls can be considered.
Those chosen will be influenced, to some extent, by the cost of purchasing, operating,
servicing, and maintaining the control. For this reason, engineering, safety, and
industrial hygiene personnel, as well as employees who operate, service, and maintain
equipment, must be involved in the noise-control plan. Employees who work with the
equipment on a daily basis will be able to provide valuable guidance on such important
matters as the positioning of monitoring indicators and panels, lubrication and servicing
points, control switches, and the proper location of access doors for operation and
maintenance. It also may be desirable to obtain the services of an acoustical consultant
to assist in the design, implementation, installation, and evaluation of these controls.
In the design and installation of engineering noise controls, ergonomics must be
considered along with optimal work efficiency. For example, work posture (sitting,
standing, bending) as well as existing environmental factors (lighting, heating, and
cooling) must be considered. This is especially true with employee enclosures or booths.
Lighting, heating, and cooling must ensure comfort and be sufficient to prevent reduction
in efficiency and work quality. Enclosures should be of adequate size and have enough
window area to prevent claustrophobia. Windows should be positioned carefully to enhance
proper usage by employees, and the glass may need to be tilted to prevent glare. In
situations where employees will be working on or around equipment fitted with engineering
controls, it is important to explain to everyone involved why the controls should not be
modified, removed, or otherwise defeated.
Administrative controls, defined as changes in the work schedule or operations which
reduce noise exposure, may also be used effectively. Examples include operating a noisy
machine on the second or third shift when fewer people are exposed, or shifting an
employee to a less noisy job once a hazardous daily noise dose has been reached.
Generally, administrative controls have limited use in industry because employee contracts
seldom permit shifting from one job to another. Moreover, the practice of rotating
employees between quiet and noisy jobs, although it may reduce the risk of substantial
hearing loss in a few workers, may actually increase the risk of small hearing losses in
A more practical administrative control is to provide for quiet areas where employees
can gain relief from workplace noise. Areas used for work-breaks and lunch rooms should be
located away from noise. If these areas must be near the production line, they should be
acoustically treated to minimize background noise levels. Much literature is available
describing methods and procedures for noise measurement and analysis, instrumentation,
engineering noise controls, performance characteristics of noise control materials, and
case histories of the implementation of noise control solutions. Suggested readings are
listed in Appendix D.
Management's primary responsibilities are to make sure that potentially controllable
noise sources are identified, and that priorities for controls are set and accomplished.
For this purpose, management needs to allocate the appropriate resources and engage
outside services or identify capable personnel in-house. It is also management's
responsibility to see that any changes of equipment or process are done only after
evaluation of their impact on employee noise exposure. The purchase of quieter new
equipment can be very helpful, but is usually accomplished only with explicit
specification, and occasionally some pressure on the equipment manufacturers. Sometimes
the company must be willing to pay more for quieter equipment, but these expenditures
should be cost-effective in the long run.
Often a noise-control effort may seem to be overwhelming. As a result, the company may
decide that noise control is not feasible and rely on hearing loss prevention measures to
prevent hearing loss. However, if noise sources are taken on one at a time, dealing with
the noisiest or easiest to quiet sources first, the problem can become manageable over
time so that hearing loss prevention measures will be needed only until the noise is
reduced to a safe level. Many times two hazards can be ameliorated at once such as in the
case of enclosing a noisy machine that generates high heat levels as well. The enclosure
can trap the noise and the heat can be vented off to the outside. The time when workplace
noise is no longer hazardous will be hastened if the control of noise from current sources
is augmented by a "buy quiet" program.
Managers may need to commit resources for in-house development of technology to control
exposure problems specific to their companies and processes. In some cases they may need
to budget for maintenance of exposure control devices to prevent their deterioration over
time. Finally, they should make sure that lunch and break areas are as free from hazards
as reasonably possible, and that other avenues of administrative controls have been
Program Implementor Responsibilities
One of the most important responsibilities of the hearing loss prevention program
implementor is to make sure that management is aware of the need for engineering controls
and their benefits. He or she should see that the company has thoroughly assessed the full
potential for using both engineering and administrative controls.
Those who implement the hearing loss prevention program will probably not actually
execute the exposure control solutions, but will provide a channel between the employees
who operate the equipment, management, and the noise control specialists. It is the job of
the implementor to make sure that communication lines are open, and that the equipment
operators are consulted in control design. Program implementors will be responsible for
making sure that employees understand the proper use of noise control devices, and for
maintaining them in good condition.
Because the employees who operate or maintain and repair the equipment are often the
ones who know most about the processes involved, they need to express their concerns and
ideas to management, the program implementor, or the noise-control engineer, so that the
noise-control devices will be as practical and effective as possible. Employees also have
the responsibility of learning to operate their machines with the noise controls in place,
of maintaining the controls properly, and of notifying the appropriate personnel when
additional maintenance is needed.
Code of Federal Regulations, Title 29, Chapter XVII, Part 1910, Subpart G, 1910.95:
sections (a) and (b).
See checklist in Appendix A of this
items no. 1-3.
See checklist in Appendix B of this guidebook,
section entitled "Engineering and Administrative
Beranek LL, ed. Noise and Vibration Control. revised. New York: McGraw Hill.
Bruce RD, Toothman EH . Engineering controls. In: Berger EH, Ward W.D, Morrill,
JC, Royster LH, eds. Noise and Hearing Conservation Manual. 4th ed. Akron, OH:
American Industrial Hygiene Assoc. Chapter 12.
Harris CM ed.  Handbook of Noise Control. 3rd ed. New York: McGraw
Hill, Chapters 26 and 30-41.
OSHA. . Noise Control: A Guide for Workers and Employers. Pub. No. 3048.
Washington, D.C. U.S. Dept. of Labor/OSHA, Office of Information.
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