In the 1960s and earlier, few people recognized that citizens might be entitled to be protected from adverse sound level exposure. Most concerted actions consisted of citizens groups organized to oppose a specific highway or airport, and occasionally a nuisance lawsuit would arise. Things in the United States changed rapidly with passage of the National Environmental Policy Act (NEPA) in 1969 and the Noise Pollution and Abatement Act (more commonly called the Noise Control Act (NCA) of 1972). Passage of the NCA was remarkable with the lack of historic organized citizen concern; however, EPA had testified before congress that 30 million Americans are exposed to non-occupational noise high enough to cause hearing loss and 44 million Americans live in homes impacted by aircraft or highway noise. NEPA requires all federally funded major actions to be analyzed for all physical environmental impacts including noise pollution, and the NCA directed the EPA to promulgate regulations for a host of noise emissions. Japan actually passed the first national noise control act, but its scope was much more limited than the U.S. law, addressing mainly workplace and construction noise.
Initially these laws had a significant effect on thoughtful study of transportation programs and also federally funded housing programs in the United States. They also gave states and cities an impetus to consider environmental noise in their planning and zoning decisions, and led to a host of statutes below the federal level. Awareness of the need for noise control was rising; in fact, by 1973 a national poll of 60,000 U.S. residents found that sixty percent of people considered street noise to have a “disturbing, harmful or dangerous” impact. This trend continued strongly throughout the 1970s in the U.S. with about half of the states and hundreds of cities passing substantive noise control laws; however noise regulation subsided sharply in 1981, when congress ended funding for the NCA. What made matters worse is that the EPA had pre-empted lower levels of government from regulating sources, so that states could not legislate in the area, for example, of truck noise emissions. Thus, in areas where the federal government had failed to promulgate clear standards (such as aircraft noise), no further progress could be made except by the FAA, who has an inherent conflict of interest regarding noise regulation.
Nevertheless some states continued to act; notably, California, carried out an ambitious plan to require its cities to establish a “Noise Element of the General Plan”, which provides guidance for land planning decisions to minimize noise impacts on the public. Many cities throughout the U.S. also have a noise ordinance, which states the allowable sound level which can cross property lines; these ordinances can be enforced with local police powers.
The following European countries emulated the U.S. national law, enacting national statutes governing noise: Netherlands (1979), France (1985), Spain (1993), Denmark (1994). In some cases unlegislated innovations have led to quieter products exceeding legal mandates (for example, hybrid vehicles or best available technology in washing machines). In any case, the legacy of the NCA has transformed irreversibly the way people think about noise and the intrinsic right to be protected from adverse sound levels.
After the passage of the NCA, EPA busily promulgated regulations setting maximum noise limits on a gamut of motor vehicles, industrial machinery and household appliances. They conducted extensive testing and involved industry in the practicality of manufacturing quieter devices. They had an influence on the future of a quieter generation of machines; however, roadway noise and aircraft noise account for the lion’s share of noise emissions, and the EPA standards for those vehicles pre-empted states from further regulating; moreover, in the case of aircraft noise, FAA had veto power over EPA recommendations, so those standards never pushed the envelope.
In the case of motor vehicles, this situation translated as follows: states could not exact a greater standard for enforcement against an individual vehicle, and interstate commerce priorities meant that guidelines for total noise exposure along federally funded highways remained guidelines and not strict standards. Despite these drawbacks, states and the public at large had a superb weapon in the review of proposed major transportation systems in the form of NEPA and the NCA. In many cases courts were able to enforce the intent of those laws to secure the redesign of roadways and transit systems to provide more noise mitigation or to select an alternative of lesser impact than the original project; in many other cases, the highway agencies simply listened to public input and acoustical scientists before finalizing highway and transit designs.
In the case of airport expansions, the power structure came down differently, because courts consistently upheld the sovereignty of the FAA over the EPA, in allowing air traffic needs to be met over environmental concerns. Thus airports were required to study impacts of air traffic and facilities expansions and provide detailed noise contour maps, but in the final analysis the EPA exposure guidelines were just that: guidelines. To make matters better, FAA created a well funded program to insulate thousands of homes in the vicinity of major airports, based upon computer modeling of alternative insulation strategies, house by house. While this program did nothing for exterior sound levels, it benefited residential interiors significantly. Beyond the U.S. activities the European countries generally lag by 10 to 20 years. For example, Britain’s National Environmental Protection Act of 1990 is stimulating research in the year 2006 aimed at setting certain definitive noise standards. Russia, China and undeveloped countries lag even further behind.
States passed two different types of legislation starting in the 1970s, echoing the federal lead in noise control. Firstly many states, with California in the vanguard, began requiring each municipality and county to have a Noise Element of the General Plan, a substantial noise data base and blueprint for making land use decisions in that jurisdiction. The Noise Element became an integral part of the municipal or county General Plan, especially in California. This document compiled a comprehensive set of measurements setting forth existing sound levels, frequently in the form of sound level contour maps to illustrate where varying sound levels fall relative to land use categories. The Noise Element further states goals for each land use class and even numerical planning standards in order to evaluate future development proposals with regard to noise pollution. Technical analysis of urban highway noise had advanced by the early 1970s to allow intricate analysis of urban planning decisions in order to plan and design urban highways and support associated noise regulations.
Cities and counties in the U.S. who either fell under state mandates or who voluntarily chose to control noise through land use decisions, were active in mapping sound levels and seeking development strategies that would minimize the number of persons exposed to harmful levels of (primarily) motor vehicle noise. One of the first cities in the U.S. to achieve a comprehensive Noise Element of the General Plan was Burlingame, California.
Principally aimed at construction noise, power equipment of individuals and unmuffled industrial noise penetrating residential areas. Thousands of U.S. cities have prepared noise ordinances that give noise control officers and police the power to investigate noise complaints and enforcement power to abate the offending noise source, through shutdowns and fines. A typical noise ordinance sets forth clear definitions of acoustics nomenclature and defines categories of noise generation; then numerical standards are established, so that enforcement personnel can take the necessary steps of warnings, fines or other municipal police power to rectify unacceptable noise generation. Ordinances have achieved certain successes but they can be thorny to implement. Many European cities are still treating noise as the U.S. did in the 1960s, as a nuisance and not as a numerical standard to be achieved.
In the case of construction of new (or remodeled) apartments, condominiums, hospitals and hotels many US states and cities have stringent building codes with requirements of acoustical analysis, in order to protect building occupants from (a) exterior noise sources and (b) sound generated within the building itself. With regard to exterior noise, the codes usually require measurement of the exterior acoustic environment in order to determine the performance standard required for exterior building skin design. The architect can work with the acoustical scientist to arrive at the best cost effective means of creating a quiet interior (normally 45 dBA). The most important elements of design of the building skin are usually: glazing (glass thickness, double pane design etc.), roof material, caulking standards, chimney baffles, exterior door design, mail slots, attic ventilation ports and mounting of through the wall air conditioners. A special case of building skin design arises in the case of aircraft noise, where the FAA has funded extensive work in residential retrofit.
Regarding sound generated inside the building, there are two principal types of transmission. Firstly, airborne sound travels through walls or floor/ceiling assemblies and can emanate from either human activities in adjacent living spaces or from mechanical noise within the building systems. Human activities might include voice, amplified sound systems or animal noise. Mechanical systems are elevator systems, boilers, refrigeration or air conditioning systems, generators and trash compactors. Since many of these sounds are inherently loud, the principle of regulation is to require the wall or ceiling assembly to meet certain performance standards (typically Sound Transmission Class of 50), which allows considerable attenuation of the sound level reaching occupants.
The second type of interior sound is called Impact Insulation Class (IIC) transmission. This effect arises not from airborne transmission, but rather from transmission of sound through the building itself. The most common perception of IIC noise is from footfall of occupants in living spaces above. This type of noise is somewhat more difficult to abate, but consideration must be given to isolating the floor assembly above or hanging the lower ceiling on resilient channel. Commonly a performance standard of IIC equal to 50 is specified in building codes. California has generally led the U.S. in widespread application of building code requirements for sound transmission; accordingly, the level of protection for building occupants has increased markedly in the last several decades.