Engineering and Administrative Controls

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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 Appendix B.

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 many workers.

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 Responsibilities

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 explored.

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.

Employee Responsibilities

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.

OSHA Requirements

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 guidebook,
items no. 1-3.
See checklist in Appendix B of this guidebook,
section entitled "Engineering and Administrative

Further Reading

Beranek LL, ed.[1988] Noise and Vibration Control. revised. New York: McGraw Hill.

Bruce RD, Toothman EH [1986]. 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. [1991] Handbook of Noise Control. 3rd ed. New York: McGraw Hill, Chapters 26 and 30-41.

OSHA. [1980]. 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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