and transportation systems to support comparisons of metrics and predictions by models).

  1. Policy agencies should conduct extensive surveys around at least six U.S. airports to generate high-quality data to populate the database. These surveys should serve as models of good survey practices, including data recording and archiving to ensure that they are useful for future studies.


This report provides information on both occupational and nonoccupational noise that can damage hearing and assesses the technologies and regulatory framework that address hazardous noise in the workplace. Current U.S. Department of Labor limits on occupational noise exposure are higher than those recommended by EPA, the National Institute of Occupational Safety and Health (NIOSH), and hearing conservation professionals worldwide, as well as current limits written into national and international standards.

Recommendation 4-1: To comply with the recommendation of the National Institute for Occupational Safety and Health, the policy of several other government agencies, and widespread national and international scientific opinion, the U.S. Department of Labor should adopt the 85-dB(A)/3-dB limit for exposure to hazardous noise. This would replace the current 90-dB(A)/5-dB requirement.

With respect to impulsive noise (a single burst or a series of bursts closely spaced or isolated) and its associated auditory hazards, the committee concludes that current damage risk criteria in the United States and internationally are inadequate and need further study.

Recommendation 4-2: The National Institute for Occupational Safety and Health should be the lead agency and should be tasked by its parent agencies (U.S. Department of Health and Human Services/Centers for Disease Control and Prevention) to develop new damage risk criteria with assistance from the military services that have experience with high-amplitude impulsive noise.


The original 1971 Occupational Safety and Health Administration noise regulation for general industry, 29 CFR 1910.95, accorded “engineering controls” (i.e., reducing the noise exposure of workers by reducing the noise of the machinery or equipment that generates the noise) primacy in reducing hazardous noise exposure in the workplace. Reviewing research and experience since the 1971 regulation, the committee concludes that engineering controls, “buy quiet” programs (programs that require or provide incentives for companies and government entities to purchase quieter equipment), or other means that reduce hazardous workplace noise provide significant long-term advantages over the use of individual hearing protection devices (HPDs) in the workplace.

The committee concludes that engineering controls of noise in the workplace should be the primary method of protecting workers from hazardous noise exposure. Accordingly, the committee recommends the following actions by U.S. government agencies, engineering and trade societies, and other stakeholders to promote the development and use of engineering controls.

Recommendation 4-3: The U.S. Department of Labor should revoke the Occupational Safety and Health Administration (OSHA) “100-dB Directive” of 1983, which effectively raised the action point for engineering control of noise from 90 to 100 dB by allowing the substitution of hearing protectors for noise control up to 100 dB and thereby devastated the market for quiet machinery and equipment. At the same time, OSHA should reconfirm that engineering controls should be the primary means of controlling noise in the workplace.

Recommendation 4-4: The National Institute for Occupational Safety and Health and the U.S. Department of Labor should develop and distribute widely an electronic database of noise control problems, solutions, and materials—taking into account the many handbooks and articles devoted to industrial noise control.

Recommendation 4-5: Engineering societies and trade organizations should develop guidelines for defining the relationship between noise emission specifications in terms of sound power level and/or emission sound pressure level and noise immission levels in industrial situations. They should provide a primer for buyers and sellers of machinery and equipment that includes: descriptions of how noise propagates in rooms; how to determine noise from a large number of machines; standards available to manufacturers and others for measuring noise emissions; and case histories of noise levels measured in in situ environments.

Recommendation 4-6: Government agencies should be instructed by a presidential directive or in congressional report language to show leadership in promoting “buy quiet” activities by developing and implementing programs for the purchase of low-noise products, as required by 42 USC 65, Section 4914. American industry should adopt “buy quiet” programs that require noise emission specifications on all new equipment and “declared values” in purchase specifications.

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