11
Summary Findings and Recommendations

This summary has been prepared to give readers a concise view of the contents of the report and the recommendations. Because of the large number of issues covered in this report and the likelihood that some readers may be interested in only one or a few chapters, findings and recommendations are also included in Chapters 3 through 10. The contents of this summary are aligned with the Executive Summary, an even shorter overview; the committee recommends that the Executive Summary be read before the findings and recommendations summarized below.

IMPROVE ENVIRONMENTAL NOISE METRICS

The committee studied the applications and limitations of existing environmental or community noise metrics. The current most widely accepted metric for characterizing the impact of environmental noise, the day-night average sound level1 (DNL) measured in decibels (dB) has both strengths and weaknesses. Yet the committee agreed that DNL remains a very useful measure for understanding, communicating, and responding to potential noise impacts on communities. Extensive research has shown that a DNL of 65 dB yields a significantly higher fraction of affected populations that are “highly annoyed” (12 to 19 percent) than a DNL of 55 dB (only 3 to 8 percent). Therefore, the committee concludes that there is sufficient evidence to justify reducing the current U.S. federal agency limit on DNL from 65 to 55 dB.


Recommendation 3-1: The federal government (e.g., agencies of the U.S. Department of Transportation with responsibilities related to noise and the U.S. Department of Housing and Urban Development) should adopt as a goal the 1974 recommendation of the Environmental Protection Agency (EPA, 1974) to limit the day-night average sound level (DNL) to 55 decibels (dB) to protect the public health and welfare. Currently, DNL (DENL in Europe), the accepted metric for characterizing the impact of community noise, shows that a large proportion of the population is highly annoyed at a DNL of 65 dB or higher.


Recent advances in the collection, storage, and analysis of noise data have led to a reexamination of the metrics developed in the 1970s or earlier and the development of new community noise metrics that more accurately reflect human responses to noise.


Recommendation 3-2: Relevant agencies of the federal government (e.g., agencies of the U.S. Department of Transportation with responsibilities related to noise, the Environmental Protection Agency, and the U.S. Department of Housing and Urban Development) should fund the development of environmental noise metrics that are more transparent and more reflective of the impact of noise on an affected population than DNL. This will require improved tools for predicting community sound pressure time histories and the development of metrics that accurately reflect the sounds people hear. A more holistic model of annoyance is also needed that incorporates situational variables that can be used to generate predictions for overall response, as well as responses of vulnerable populations (e.g., elderly people, sick people, children, and noise-sensitive individuals). International cooperation in this effort will facilitate the development of national and international standards for calculating metrics and should include open-source code to facilitate broad implementation of the metrics. Certain measures should be taken to facilitate this development:

  1. The international noise control engineering community should develop an open, collaborative data-sharing environment in which researchers can deposit and access data from community noise surveys (e.g., data from surveys of acoustic, environmental, community,

1

The day-night average sound level (DNL) is the average sound level for a 24-hour day, after addition of 10 decibels to levels from midnight to 0700 hours and from 2200 hours (10 p.m.) to midnight.



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11 Summary Findings and Recommendations This summary has been prepared to give readers a concise (DNL) to 55 decibels (dB) to protect the public health and view of the contents of the report and the recommendations. welfare. Currently, DNL (DENL in Europe), the accepted Because of the large number of issues covered in this report metric for characterizing the impact of community noise, and the likelihood that some readers may be interested in shows that a large proportion of the population is highly only one or a few chapters, findings and recommendations annoyed at a DNL of 65 dB or higher. are also included in Chapters 3 through 10. The contents of this summary are aligned with the Executive Summary, an Recent advances in the collection, storage, and analysis even shorter overview; the committee recommends that the of noise data have led to a reexamination of the metrics de- Executive Summary be read before the findings and recom- veloped in the 1970s or earlier and the development of new mendations summarized below. community noise metrics that more accurately reflect human responses to noise. IMPROVE ENVIRONMENTAL NOISE METRICS Recommendation 3-2: R elevant agencies of the fed - The committee studied the applications and limitations eral government (e.g., agencies of the U.S. Department of of existing environmental or community noise metrics. The Transportation with responsibilities related to noise, the current most widely accepted metric for characterizing the Environmental Protection Agency, and the U.S. Depart- impact of environmental noise, the day-night average sound ment of Housing and Urban Development) should fund the level1 (DNL) measured in decibels (dB) has both strengths development of environmental noise metrics that are more and weaknesses. Yet the committee agreed that DNL remains transparent and more reflective of the impact of noise on an a very useful measure for understanding, communicating, affected population than DNL. This will require improved and responding to potential noise impacts on communities. tools for predicting community sound pressure time histories Extensive research has shown that a DNL of 65 dB yields a and the development of metrics that accurately reflect the significantly higher fraction of affected populations that are sounds people hear. A more holistic model of annoyance “highly annoyed” (12 to 19 percent) than a DNL of 55 dB is also needed that incorporates situational variables that (only 3 to 8 percent). Therefore, the committee concludes can be used to generate predictions for overall response, as that there is sufficient evidence to justify reducing the current well as responses of vulnerable populations (e.g., elderly U.S. federal agency limit on DNL from 65 to 55 dB. people, sick people, children, and noise-sensitive individu- als). International cooperation in this effort will facilitate Recommendation 3-1: The federal government (e.g., agen- the development of national and international standards for cies of the U.S. Department of Transportation with responsi- calculating metrics and should include open-source code to bilities related to noise and the U.S. Department of Housing facilitate broad implementation of the metrics. Certain mea - and Urban Development) should adopt as a goal the 1974 sures should be taken to facilitate this development: recommendation of the Environmental Protection Agency (EPA, 1974) to limit the day-night average sound level 1. The international noise control engineering communi- ty should develop an open, collaborative data-sharing environment in which researchers can deposit and 1The day-night average sound level (DNL) is the average sound level for access data from community noise surveys (e.g., data a 24-hour day, after addition of 10 decibels to levels from midnight to 0700 from surveys of acoustic, environmental, community, hours and from 2200 hours (10 p.m.) to midnight. 7

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8 TECHNOLOGY FOR A QUIETER AMERICA and transportation systems to support comparisons of the committee concludes that engineering controls, “buy metrics and predictions by models). quiet” programs (programs that require or provide incen- 2. Policy agencies should conduct extensive surveys tives for companies and government entities to purchase around at least six U.S. airports to generate high- quieter equipment), or other means that reduce hazardous quality data to populate the database. These surveys workplace noise provide significant long-term advantages should serve as models of good survey practices, over the use of individual hearing protection devices (HPDs) including data recording and archiving to ensure that in the workplace. they are useful for future studies. The committee concludes that engineering controls of noise in the workplace should be the primary method of protecting workers from hazardous noise exposure. Accord- STRENgTHEN THE REguLATORy FRAMEWORK FOR ingly, the committee recommends the following actions by HAZARDOuS NOISE U.S. government agencies, engineering and trade societies, This report provides information on both occupational and and other stakeholders to promote the development and use nonoccupational noise that can damage hearing and assesses of engineering controls. the technologies and regulatory framework that address Recommendation 4-3: The U.S. Department of Labor hazardous noise in the workplace. Current U.S. Department of Labor limits on occupational noise exposure are higher should revoke the Occupational Safety and Health Ad - than those recommended by EPA, the National Institute of ministration (OSHA) “100-dB Directive” of 1983, which Occupational Safety and Health (NIOSH), and hearing con- effectively raised the action point for engineering control servation professionals worldwide, as well as current limits of noise from 90 to 100 dB by allowing the substitution of written into national and international standards. hearing protectors for noise control up to 100 dB and thereby devastated the market for quiet machinery and equipment. Recommendation 4-1: To comply with the recommenda- At the same time, OSHA should reconfirm that engineering tion of the National Institute for Occupational Safety and controls should be the primary means of controlling noise Health, the policy of several other government agencies, and in the workplace. widespread national and international scientific opinion, the Recommendation 4-4: The National Institute for Occupa- U.S. Department of Labor should adopt the 85-dB(A)/3-dB limit for exposure to hazardous noise. This would replace the tional Safety and Health and the U.S. Department of Labor current 90-dB(A)/5-dB requirement. should develop and distribute widely an electronic database of noise control problems, solutions, and materials—taking With respect to impulsive noise (a single burst or a series into account the many handbooks and articles devoted to of bursts closely spaced or isolated) and its associated audi- industrial noise control. tory hazards, the committee concludes that current damage Recommendation 4-5: Engineering societies and trade risk criteria in the United States and internationally are inadequate and need further study. organizations should develop guidelines for defining the re- lationship between noise emission specifications in terms of Recommendation 4-2: The National Institute for Occu- sound power level and/or emission sound pressure level and pational Safety and Health should be the lead agency and noise immission levels in industrial situations. They should should be tasked by its parent agencies (U.S. Department provide a primer for buyers and sellers of machinery and of Health and Human Services/Centers for Disease Control equipment that includes: descriptions of how noise propa- and Prevention) to develop new damage risk criteria with gates in rooms; how to determine noise from a large number assistance from the military services that have experience of machines; standards available to manufacturers and others with high-amplitude impulsive noise. for measuring noise emissions; and case histories of noise levels measured in in situ environments. PROMOTE THE uSE OF ENgINEERINg CONTROLS TO Recommendation 4-6: Government agencies should be REDuCE HAZARDOuS NOISE instructed by a presidential directive or in congressional The original 1971 Occupational Safety and Health Ad- report language to show leadership in promoting “buy quiet” ministration noise regulation for general industry, 29 CFR activities by developing and implementing programs for 1910.95, accorded “engineering controls” (i.e., reducing the purchase of low-noise products, as required by 42 USC the noise exposure of workers by reducing the noise of the 65, Section 4914. American industry should adopt “buy machinery or equipment that generates the noise) primacy quiet” programs that require noise emission specifications in reducing hazardous noise exposure in the workplace. Re- on all new equipment and “declared values” in purchase viewing research and experience since the 1971 regulation, specifications.

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 SUMMARY FINDINGS AND RECOMMENDATIONS DEVELOP AND DEPLOy TECHNOLOgIES FOR NOISE organizations and academic institutions, research should CONTROL focus on the complex interrelationships between engine and airframe and the importance of reducing each constituent The committee assessed new technologies in materials noise source to reduce the overall noise signature of aircraft. and systems for controlling noise from a large variety of These projects should develop improved prediction tools, for sources. There are enormous disparities among programs, example, for advanced propulsion designs; acoustic scatter- facilities, and resources for addressing noises of different ing and propagation models, including weather and terrain types. For example, although engineering tools may be models; models of the effects of interactions between engine available for reducing aircraft noise and highway noise, the installation and airframe configuration; and benchmark mea- former has been deemed a national priority, while the latter surements necessary for the development and validation of has received less attention. Resources allocated for noise these advanced tools. reduction are not always commensurate with noise exposures and impacts. Recommendation 5-2: The Federal Aviation Administra- Aircraft noise control technology is much more advanced tion should continue to fund the development of novel op- than technologies for addressing other noise sources, and erational and air traffic management procedures to minimize the funds expended to reduce the noise of airplanes them- noise and should work with NASA and industry to make selves as well as mitigation measures around airports is far intelligent trade-offs between competing noise mitigation greater than for other noise sources. Road traffic noise has and chemical pollution goals. been controlled mostly by constructing noise barriers, but work is being done on promising technologies for reducing Reducing Road Traffic Noise noise generated by tire/road interaction. Technologies are available for reducing noise from rail-guided vehicles, and Recommendation 5-3: Current activities of the Federal these will become more important as the nation develops Highway Administration and several states to investigate light rail systems and high-speed trains. Technologies for noise reduction through new pavement design should be the built environment will also become more important as continued and expanded to speed up development and ap- building construction is driven by Leadership in Energy and plication of new technologies. Studies on the durability of Environmental Design (LEED) certification and “green” pavement surfaces are essential, because durability has a principles. Active controls of sound and vibration have been direct effect on the life-cycle costs of applying quiet pave- under development for many years, but few products on the ment technology, which has the potential to reduce noise market have incorporated them, and many barriers must still where barriers are not feasible—for example, where homes be overcome. are located on a hillside overlooking a busy highway. Many tools for designing and developing quieter prod- ucts have become available in the past few decades, driven Reducing Rail Noise largely by increases in computational power and reductions in computational costs. Even so, access to new tools is as Recommendation 5-4: P lanning tools available from uneven as the allocation of resources; corporate budgets for modal agencies of the U.S. Department of Transportation, capital equipment are generally tight, and there is competi- such as the Federal Railroad Administration and the Federal tion between departments for available funds. Furthermore, Transit Administration, should be used in planning new rail organizations that are doing only routine testing of products transportation systems, and supplemental metrics should be according to national and international standards find ex- developed and used to estimate the effects of noise on people. pensive new tools hard to justify. Thus, even though noise The public would benefit if warning horns were made more mechanisms in aircraft, automobiles, rapid transit and trains, directional; research and development related to warning consumer products, and industrial machinery are fundamen- horn directivity should be undertaken to better understand tally similar, the availability and application of tools for ad- the effects on safety and benefits to the public. dressing them are not. The committee recommends that ways be found to give industry and academia access to these tools Reducing Noise in Buildings for the benefit of manufacturers, workers, and the public. Recommendation 5-5: The acoustics and noise control Reducing Aircraft Noise communities should actively promote the inclusion of noise criteria in requirements for Leadership in Energy and En- Recommendation 5-1: T he National Aeronautics and vironmental Design (LEED) certification of buildings, not Space Administration (NASA) should continue to fund col- only to improve the noise environment but also to ensure laborative projects by engine, airframe, and aircraft systems that the acoustical environment is not degraded. Design manufacturers. Drawing on expert knowledge in research standards (e.g., building codes) must be improved to ensure

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40 TECHNOLOGY FOR A QUIETER AMERICA that good acoustical practices are followed in the construc- buried in product literature and reported using different noise tion of buildings. m etrics, making it difficult for consumers to compare noise levels at the time of purchase. Thus, consumers are Recommendation 5-6: The National Institutes of Health unable to make informed decisions on the noise emission and/or the Facilities Guidelines Institute should fund the de- of a product. This problem could be corrected if product velopment of improved materials for hospital environments, noise levels were prominently displayed and manufacturers where traditionally used materials may harbor and promote adopted a system of self-enforcement. the growth of bacteria and other harmful biological agents. American manufacturers have the ingenuity to design quiet products. However, manufacturers and trade associa- tions, as well as the voluntary standards community, have Advancing Active Noise Control been unable to agree on a uniform standard for measuring Recommendation 5-7: Research agencies should fund and labeling product noise. university research on active noise control to address situa- Recommendation 6-1: T he Environmental Protection tions where the use of traditional noise-control materials is problematic or where they are not suitable for attenuating Agency should encourage and fund the development of a uni- noise in the appropriate frequency range. Investigations into form system of labeling product noise. The system should be hybrid active-passive and adaptive-passive noise control self-enforced by manufacturers but should have strict rules systems and the development of low-cost microphones and and penalties if products are deliberately mislabeled. The loudspeakers that can be used in hostile environments should rules should specify standard methodologies for measuring also be funded. product noise. Uncertainties in noise emission values should be acknowledged. Product noise labels should be prominent- ly displayed so that consumers can make informed purchas- DEVELOP PRODuCT NOISE EMISSION STANDARDS ing decisions. In a world with proliferating eco-labels and AND REguLATIONS different requirements, international cooperation to develop The need for noise emission standards is recognized one label recognized worldwide would be of great benefit to worldwide, especially in the European Union (EU). This American manufacturers and consumers everywhere. need has made the International Organization for Standard- Recommendation 6-2: Government, trade associations, ization, and to some extent the International Electrotechni- cal Commission, leaders in the standards community. ISO and industry should fund the participation of U.S. technical standards committees have superseded many American- experts on standards bodies that develop international stan- based standards committees and organizations that U.S. dards for determining product noise emissions. manufacturers have relied on in the past. America’s voice Recommendation 6-3: The National Institute of Standards on the ISO standards committees is weakened by the lack of U.S. manufacturers’ leadership in ISO working groups. and Technology should take the lead in providing assistance America has only a single vote, the same as every member to American manufacturers with noise regulation compli- country in the EU. ance by establishing a database of information on U.S. The EU has been a leader in the development of noise and international product noise emission standards and regulations based on these standards. These regulations are requirements. more extensive than those that exist in the United States, Recommendation 6-4: To establish their credibility, orga- and consequently European manufacturers have gained a competitive advantage over their U.S. counterparts in nizations that determine noise emission data according to meeting demand for low-noise machinery and other prod- a certain standard as part of a voluntary labeling program ucts worldwide. It is important to note that, although more should be accredited to test products. Managers at the stringent noise requirements can sometimes be a burden National Institute of Standards and Technology and its Na- for manufacturers, they can also encourage innovation. A tional Voluntary Laboratory Accreditation Program should manufacturer’s desire to design a low-noise machine for promote their accreditation program, especially in industrial sale in world markets is a positive force that could lead to laboratories. the introduction of quiet products into American markets and provide an incentive for manufacturers and purchasers uSE COST-BENEFIT ANALySIS AS A TOOL FOR NOISE to cooperate in “buy quiet” programs. MITIgATION At the time of purchase, consumers rank noise as one of the top five characteristics when comparing product perfor- The committee considered cost-benefit analysis for dif- mance. Other concerns are energy efficiency, cost, reliability, ferent noise mitigation options in a broad context and in the and serviceability. Noise levels for U.S. products are often specific context of reducing noise generated by interactions

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4 SUMMARY FINDINGS AND RECOMMENDATIONS between vehicle tires and road surfaces. At highway speeds • coordination and cooperation among existing inter- this tire/road interaction noise dominates noise emissions agency groups concerned with noise from vehicles, and efforts are being made to design road • clear delineation of the roles of federal agencies, as surfaces and tires that minimize this noise. The efforts of well as state and local governments the Federal Aviation Administration to develop a cost-benefit • assisting American industry in lowering noise levels approach to analyze noise around airports could help in the in the U.S. workplace and developing industrial and development of a similar project to analyze options for re- consumer products with noise emissions that are com- ducing highway noise. petitive with foreign products • development of international standards for the mea- Recommendation 7-1: A f ormal cost-benefit analysis surement and labeling of noise emissions should be performed to compare the costs and benefits of • active U.S. participation in the harmonization of noise using pavement technology for noise reduction with the costs emission requirements worldwide and benefits of installing noise barriers. This cost-benefit • development of metrics for environmental noise that analysis should be a cooperative effort of the Federal High- truly represent community response to noise way Administration, U.S. Environmental Protection Agency, • ongoing assessment of the costs and benefits of noise and the several states with technology programs in road sur- control face design. Inputs to the analysis should include data from • increased research on the health effects of noise, espe- analyses of noise reduction efforts around airports. cially nonauditory effects STRENgTHEN THE ROLE OF gOVERNMENT EDuCATE MORE NOISE CONTROL ENgINEERS In some areas—notably aircraft noise, occupational noise, The committee reviewed the state of noise control engi- and highway noise that can be reduced by barriers—govern- neering education in the United States and concludes that the ment regulation has been instrumental in reducing noise. But nation must educate more specialists in the field and provide this report shows that improvements can be made in other basic knowledge of the principles of noise control engineer- ways as well. For example, authority for cost-benefit analy- ing to individuals trained as specialists in other engineering ses, interagency projects, and the dissemination of public disciplines. Undergraduate education in noise engineering information on noise was given to the EPA by Congress. Be- varies greatly from institution to institution, both in terms cause of a lack of funding, however, EPA has been unable to of the department in which it is housed and in the courses carry out these activities. The study committee recommends offered. Funding for noise control engineering programs at changes that will make it easier for the federal government universities is problematic, and support for graduate students to improve the nation’s noise climate and with it the lives of to assist in research (or teaching) and to develop a new cadre American citizens. of professionals is inadequate. The multidisciplinary nature of noise control engineering Recommendation 8-1: T he Environmental Protection poses challenges for engineering practice and for lifelong Agency should carry out its coordinating function under learning. Elements of noise control engineering degree 42 USC 65, Section 4903. The agencies with noise-related programs should be formally taught by faculty in academic activities include the U.S. Department of Defense, U.S. De- units or departments (in engineering, physical sciences, and partment of Transportation, U.S. Department of Labor, U.S. architecture) in an intra- or interdisciplinary way. Major Department of Commerce, U.S. Department of Health and professional societies (such as American Institute of Aero- Human Services, U.S. Department of Housing and Urban nautics and Astronautics, American Society of Mechanical Development, and the National Science Foundation. Engineering, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Institute of Noise Control Recommendation 8-2: Congress should pass legislation Engineering of the USA, Society of Automotive Engineers) and provide the necessary funds to establish the Environmen- and other stakeholders should organize symposia (or special tal Protection Agency as the lead agency in the development sessions in regular conferences) where leading academic of a cooperative effort on noise measurement, abatement, and industry leaders can propose and refine curricula and and control involving federal agencies, state governments, suggest improvements in teaching methods and delivery industry, consulting firms, and academia. An EPA office mechanisms. Collaboration among academic, research, and should implement 42 USC 65, Section 4903, and the legisla- industry leaders will be necessary for the development of tion should expand the authority already given by Congress interesting case studies or practice modules that could then to ensure that the agency can effectively manage a program be disseminated to teachers of undergraduate courses. to meet the following objectives: Funding is particularly important for research on envi- ronmental noise, which encourages interdisciplinary col-

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4 TECHNOLOGY FOR A QUIETER AMERICA laboration between acousticians, engineers, social scientists, organizations to develop labeling methodology for specific psychologists, sociologists, and medical scientists to develop products because of the wide variety of products and noise new metrics for evaluating the impact of noise, including an- measurement methods. noyance, speech and communications interference, cognitive Recommendation 10-1: The Environmental Protection impairment, sleep disturbance, and health effects. Agency should take the following actions under the authority Recommendation 9-1: Academic institutions should offer of 42 USC 65, Section 4913, to improve public information an undergraduate course in noise control engineering, broad- and education on the effects of noise and the most effective en the scope of the engineering curriculum, and increase the means of controlling noise: pool of engineering graduates who are equipped to design for low-noise emissions. The course could be offered as an • Conduct a survey of all activities by federal agencies elective in a bachelor’s degree program or as part of a minor related to noise, and publish URLs that provide infor- (e.g., in acoustics or interdisciplinary studies). mation of interest to the public. • Develop a categorized list of stakeholders with in- Recommendation 9-2: Graduate-level noise control cours- terests in noise (e.g., professional societies, scientific es should provide a balance between theory and engineering societies, citizens groups). practice without sacrificing academic rigor. The committee • Help organize a coalition of current stakeholders with strongly encourages the establishment of graduate intern- the goal of improving the availability of information ships in industry and government agencies and thesis re- on noise to the public. search programs to motivate students and to build a cadre • Develop educational materials to inform the public of of future noise control engineers. the health effects of noise, especially noise-induced hearing loss and cardiovascular effects. Recommendation 9-3: Federal agencies, private compa- • Develop information to help the public understand the nies, and foundations with a stake in noise control should benefits of using personal hearing protection devices. provide financial support for graduate students who assist in • Provide information on the selection and use of hearing research on, and the teaching of, noise control engineering. protection devices, making intelligent decisions about This support is crucial for the development of noise control frequenting high noise exposure events, the impor- professionals and noise control educators. tance of reducing noise exposures by buying quieter products, and being vigilant and active in public policy decision making about community noise zoning is- IMPROVE PuBLIC INFORMATION ON THE EFFECTS sues. OF NOISE AND NOISE CONTROL Recommendation 10-2: Engineering professional societies The U.S. Code (42 U.S.C. Section 4913) requires that EPA “develop and disseminate information and educational such as the American Institute of Aeronautics and Astronau- materials to all segments of the public on the public health tics, the American Society of Mechanical Engineering, Amer- and other effects of noise and the most effective means for ican Society of Heating, Refrigerating and Air-Conditioning noise control, through the use of materials for school curri - Engineers, Society of Automotive Engineers, and Institute cula, volunteer organizations, radio and television programs, of Noise Control Engineering of the USA should develop publication, and other means.” At this time, however, EPA engineering information on noise control to help the public does not have the internal resources to create a large public understand techniques for reducing noise emissions. information program, and it is likely that much of the effort will have to be done through contractors. REFERENCE The labeling of product noise emission levels should be EPA (U.S. Environmental Protection Agency). 1974. Information on Levels a critical aspect of a program designed to benefit the public of Environmental Noise Requisite to Protect Public Health and Welfare and enable people to make informed purchasing decisions. with an Adequate Margin of Safety. Document 550/9-74-004. Available Although EPA has labeling authority, it is more practical for online at http://www.nonoise.org/library/leels74/leels74.htm. professional organizations, trade associations, and standards