This chapter gives a few examples of sources of noise in the community (broadly defined). Noise from aircraft operations is an important source of community noise, and three examples are given: a noise program at a well-established airport, an example of “growing pains” around a relatively new airport, and a situation where a change in policy created problems at relatively low levels of noise. Other examples include noise along the nation’s highways, noise from rail transportation, noise in urban areas (e.g., New York City), noise in national parks, noise from industrial facilities, and consumer product noise.
The U.S. Environmental Protection Agency’s “Levels Document” adopted 55 dB as the day-night average sound level (DNL) that would protect the public with an adequate margin of safety (EPA, 1974). However, according to the Federal Aviation Administration (FAA), a noise-impacted area is that inside the 65-dB DNL contour. The noise level in a community near an airport is generally defined by contours of equal DNL around the airport. Impacted areas are generally eligible for sound mitigation with insulation of homes and schools using FAA funding.
According to a report to Congress by the FAA, there has been a 95 percent reduction in the number of people affected by aircraft noise in the past 35 years (FAA, 2004). In 2000 approximately 500,000 people were exposed to a DNL of more than 65 dB and approximately 5 million people were exposed to a DNL of 55 dB.
Although the extent of exposure to aircraft noise has been greatly reduced, the 1974 EPA report stated that “aircraft noise is the single most significant local objection to airport expansion and construction.” Some of the problems around the nation’s airports are described below.
O’Hare International Airport
The O’Hare Noise Compatibility Commission (ONCC) works in the Chicago metropolitan area on problems regarding noise levels at O’Hare International Airport. ONCC considers and recommends operational programs to reduce aircraft noise impacts, evaluates reports from the Airport Noise Monitoring System, and works on noise abatement issues with air traffic controllers, FAA representatives, airline pilots, and community leaders. The ONCC issues a monthly report that contains information about runway usage, complaints, and noise levels at 37 different locations in the communities around the airport. The reports are linked to the ONCC home page (http://www.oharenoise.org).
ONCC has tracked phone call complaints about aircraft noise though its hotline since 1997, and its efforts have resulted in a reduction of calls from 25,773 in 1998 to 3,067 in 2004 (Mulder, 2005).1 More recent data show that calls in 2005, 2006, and 2007 numbered 1,958, 1,362, and 1,248, respectively. More information about the activities of ONCC can be found on the commission’s homepage and in Mulder (2005). ONCC also monitors the FAA’s Residential Sound Insulation Program for communities around O’Hare. For a bibliography on noise issues around airports, see http://airportnoiselaw.org/biblio.html.
Denver International Airport
In 1997, 22 residents living near Denver International Airport (DIA) filed suit against the city of Denver for allowing what they claimed was excessive noise. The residents, who lived 2 to 6 miles from the airport, alleged that “high levels
of noise, pollution, and vibrations on plaintiffs’ property” devalued their homes (Denver Post, 1997).
In 2005 the developer of a $1.5 billion project called High Point near DIA planned to build the first of 3,000 homes about 2.5 miles from the end of a planned runway, making future noise complaints almost inevitable (Denver Post, 2005). Buyers were warned they would be moving into an area under aircraft flight paths, but demand for the homes was expected to be high. To protect buyers, homes were built with triple-pane windows, extra insulation, and central air conditioning.
A report in 2005 prepared by DIA’s noise consultants showed that a fully constructed airport would put a noise limit line that would serve as a barrier to residential development right through the High Point project (Denver Post, 2005). The Denver City Council was concerned that occupants of the 3,000 homes in High Point might exert enough political pressure to keep the airport from being completed as envisioned.
More recently, the Denver International Airport Partnership has followed other airports (such as Washington Dulles International Airport) in providing guidelines for prospective homeowners about future development at the airport to head off potential problems (Denver Post, 2006). When DIA is fully built, it could expand from handling 43 million passengers in 2005 to more than 120 million passengers annually.
In 2006 about 320,000 people lived within 15 miles of the airport, and by 2030 the same zone is expected to have more than 500,000 people, according to the Denver Regional Council of Governments (Denver Post, 2006). Contracts for homes near the airport include a legal disclosure that buyers must sign, and some include easements for overhead traffic, precluding residents from suing because of aircraft noise.
East Coast Plan
The “East Coast Plan” developed by the FAA in 1987 to reduce flight delays changed flight paths across southern New Jersey and dispersed them over a larger area of the state. The plan affected small communities that had complained, not about high levels of noise but about the presence of a few aircraft where none had been previously. This is a good example of communities finding low levels of noise objectionable, when even lower levels existed before a change in policy.
SURFACE TRANSPORTATION NOISE
Corbisier (2003) states that “according to the most recent data available from 1987, noise from highway traffic affects more than 18 million people in the United States.” This illustrates both the extent of highway traffic noise and the fact that it has been many years since a systematic study of such noise has been done. It is more difficult to assess the impact of railway noise (see Chapter 5). A reasonable estimate is that 10 million people are affected by railway noise, including 6.5 million by train horns at rail/highway crossings.
The current solution to specific vehicle noise emission problems on highways is to construct noise barriers—solid obstructions built between a highway and nearby homes. Effective barriers can reduce noise levels by 10 to 15 dB, cutting the loudness of traffic noise approximately in half (10 dB) for people who live in close proximity to the barrier. A barrier can be a mound of earth along the side of the road (an earth berm), a relatively high vertical wall, or an earth berm combined with a shorter vertical wall above. Earth berms can be attractively landscaped but require large land areas at the base on both sides of the barrier configuration. Walls are limited to about 8 meters in height and can be made of wood, stucco, concrete, masonry, metal, or other materials.
There are no Federal Highway Administration (FHWA) requirements for the type of material used in the construction of noise barriers. Materials are chosen by the state highway administration but must meet FHWA specifications in terms of rigidity and density. Whatever material is chosen must be rigid enough and of sufficient density to provide a transmission reduction of 10 dB compared with the noise diffracted over the top of the barrier.
FHWA uses the following additional criteria for determining the feasibility of noise barriers: a barrier must be high enough and long enough to block the view of the road; noise barriers do very little good for homes on a hillside overlooking a road or for buildings that rise above the barrier; a noise barrier can achieve a 5-dB noise reduction when it is tall enough to break the line of sight from the highway, and it can achieve an additional 1.5 dB of noise reduction for every meter of height above the line of sight (with a maximum theoretical total reduction of 20 dB). FHWA’s rule of thumb is that a barrier should extend four times as far in each direction as the distance from the receiver to the barrier. Disruptions in noise walls for driveways or street intersections destroy their effectiveness. Moreover, in some areas, where homes are far apart, the cost of a barrier may be prohibitive.
The construction of noise barriers has always been a cooperative effort between state departments of transportation and FHWA, and states have a great deal of flexibility in designing and building noise barriers. Some states have built many noise barriers, and some have built none. Through the end of 2004, 45 state departments of transportation and the Commonwealth of Puerto Rico had constructed more than 2,205 linear miles of barriers at a cost of more than $2.6 billion ($3.4 billion in 2004 dollars). Five states and the District of Columbia have not constructed any noise barriers (FHWA, 2009).
Noise barriers tend to provide relief for a relatively small number of people in a given area, but the noise reductions are probably greater than those that could be achieved with modern pavement technology. However, the number of people
who could potentially get relief from improvements in road surfaces is probably greater than the number of people who get relief from barriers.
FHWA currently does not recognize porous road surfaces as a solution to the highway noise problem; however, the agency does sponsor Quiet Pavement Pilot Programs to investigate their feasibility (Ferroni, 2007).2 The costs and benefits of porous road surfaces are discussed in Chapter 7.
Noise from construction equipment has been a problem, especially in urban areas, for many years. Typical noise sources include jack hammers, compressors, pile drivers, excavators, electric generators, and various types of construction vehicles. Planning for noise control must start with planning for the project itself, and mitigation techniques include noise reduction at the source, construction of temporary noise barriers, and restriction of operating hours. The Federal Highway Administration has produced the Construction Noise Handbook (FHWA, 2006), which identifies many of the problems with construction noise. One recent example of control of construction noise is work done in connection with the Central Artery/Tunnel Project in Boston (Thalheimer, 2000, 2001). A second example is the recent New York City noise code described in the section below on urban noise. The code contains many limits on construction noise. The regulations have been described by Thalheimer and Shamoon (2007).
Rail systems are a growing component of the transportation system in the United States because of their demonstrated efficiency in energy use for transporting people and goods. As oil becomes more expensive and interest in green economies increases, rail systems can be expected to expand. Commuters are opting for rail transit in urban areas, resulting in higher ridership each year. Amtrak’s portion of intercity trips is growing in both the East Coast and the West Coast corridors. Freight railroads, which have been running at capacity, carry bulk cargo more efficiently than any other transportation mode. As rail transportation increases, an increase in noise exposure in and around transit and railroad facilities can be expected.
NOISE IN URBAN AREAS
Because there have been several recent surveys of noise in New York City, and because a new noise code went into effect in 2007, New York City is often used as an example of the problems associated with dealing with noise in an urban area. The first 10 noise sources in New York City that bother residents were found by Bronzaft and Van Ryzin (2007) to be:
car stereos or boom cars
rowdy passersby or people hanging out
neighbors’ activity or voices
highway or street traffic
sirens from police cars, fire trucks, etc.
neighbors’ music, TV, or radio
construction or repair work
It is difficult to describe many of these sources in terms of an environmental noise metric such as day-night average sound level. Consequently, the extent of noise impact is assessed in terms of the number of complaints received.
On August 17, 2005, Mayor Michael Bloomberg called a press conference to discuss the city’s noise code. He said that between June 2004 and August 2005 the city’s government services hotline received 410,000 noise complaints, making noise the number one complaint to the hotline. Online surveys conducted in collaboration with the Council on the Environment of New York City have been used to assess both the sources of urban noise and the number of complaints (Bronzaft and Van Ryzin, 2007). Surveys have focused on behavioral and emotional consequences of neighborhood noise, complaints about noise, specific sources of noise in communities, and general perceptions of neighborhood noise (Bronzaft and Van Ryzin, 2004, 2006). The surveys have shown that New Yorkers are bothered more frequently by noise and are more likely to lodge a complaint about it than respondents to similar surveys in other parts of the country (Bronzaft and Van Ryzin, 2004).
The top noise sources for New Yorkers and people nationwide that were most associated with behavioral and emotional consequences are rowdy passersby, neighbors’ activities or voices, car stereos, car horns, motorcycles, and back-up beeps. NYC residents also report more frequent behavioral and emotional consequences from noise than respondents nationwide; they are more likely to close their windows, have trouble relaxing, lose sleep, and have trouble reading. Similarly, New Yorkers are more likely to feel annoyed, angry, helpless, upset, and tired because of community noise. “These findings should demonstrate to public officials that New Yorkers cannot find the peace and quiet in their homes that they deserve” (Bronzaft and Van Ryzin, 2006).
In response to NYC noise issues, Mayor Bloomberg asked the city’s Department of Environmental Protection (DEP) to revise the noise code, and on December 29, 2005,
he signed a new version into law, which became effective on July 1, 2007. The city’s DEP, which is responsible for noise regulation, has developed a brochure that provides a brief overview of the new code. (For the full text, see http://www.nyc.gov/html/dep/pdf/law05113.pdf.)
Important methods in the new code for controlling urban noise include specification of sound pressure level limits at certain distances for sources such as construction equipment, limits on operating hours, limits on noise from some sources that are “plainly audible” at a certain distance, and limits on some sources in terms of decibels above ambient noise. The metric day-night average sound level is not used in the code. Bronzaft and Van Ryzin note that the passage of a noise code will not have the desired impact unless it is supplemented by educational materials on the hazards of noise, noise protection, and protecting the rights of others to quiet (CENYC, 2009). They also recommended that the city council consider legislation that calls for the enforcement of apartment leases guaranteeing residents the right to quiet and include discussions of floor coverings, slamming of doors, and young children running around excessively.
NOISE IN QUIET ENVIRONMENTS
Recreational noise has been the subject of three special issues of Noise Control Engineering Journal (NCEJ, 1999). In an excellent article, Sutherland (1999) discusses how to measure, evaluate, and preserve naturally quiet areas. More recently, Miller (2003, 2008) has written about the effects of transportation noise in recreational areas and problems with the metrics used to measure noise levels in quiet areas.
Rossman (2005)3 describes the Natural Sounds Program of the National Park Service (NPS) and lists the following issues that affect implementation of a noise policy in naturally quiet areas:
There is no recognized “legal” standard for ambient noise in national parks.
“Traditional” acoustic metrics are not adequate for measuring impacts on park “soundscape” resources.
Many parks are already “noisy.”
Many sound sources originate outside park boundaries.
Little information is available on the kinds of noise that disturb wildlife, and most sound data and models are weighted for human hearing.
Metrics used to measure noise levels in national parks have received much attention in the past few years, primarily because of inherent conflicts among park visitors—those engaged in activities that produce nonnatural sounds (e.g., users of personal watercraft and snowmobiles, air tours) and those who seek quiet and solitude (hikers, row boaters, campers). Nonnatural sounds also may conflict with the legislative mandates that established the park or with NPS management objectives of protecting natural sounds as a specific park resource. The NPS maintains a website devoted to natural sounds with a link to sources of human sounds (NPS, 2009).
Sources of intrusive noise include snowmobiles and other off-road vehicles, aircraft (including commercial aircraft, air tours, and private aircraft), and watercraft (including motor boats, personal watercraft, and other water vehicles). Aircraft overflights and their effects on national parks are discussed in a report to Congress (DOI, 1995).
In some parks, noise from road traffic is an issue, particularly when the only access to quiet areas is by means of a motor vehicle; not everyone is capable of hiking or skiing into naturally quiet areas. Thus, conflicts can arise even among groups of park users who have the same objectives—enjoyment of wilderness areas—but use different means of travel.
Although the day-night average sound level, DNL, is widely used to quantify community response to noise—usually in terms of the average percentage of the population likely to be highly annoyed—other factors must be considered in considering noise in naturally quiet areas. The overall goal might be described as protecting, maintaining, or restoring soundscapes appropriate to the park setting. Park soundscapes may be not only natural but also cultural (e.g., the drumbeat of a sacred tribal dance) or historical (e.g., cannon fire at a Civil War battlefield). Decisions about the appropriate soundscape for a given park area depend not only on visitor perception/satisfaction but also on judgments by park management.
One way to assess visitors’ reactions to quiet spaces is to query them by means of a survey about their degree of satisfaction with the environment. A scale of “completely satisfied” to “completely dissatisfied” is more likely to yield valid results than questions about “annoyance.” A promising alternative measure is the visitor-reported degree of “interference with the appreciation of natural quiet and the sounds of nature” (DOI, 1995; Miller, 1999).
Schomer has suggested an alternative; he argues that sound-quality techniques, which are widely used in the automotive industry and by product manufacturers (see Chapter 5), are more appropriate for measuring noise levels in parklike settings (Schomer, 2009; Schomer et al., 2008).
NOISE FROM INDUSTRIAL FACILITIES
Industry and industry regulators need better guidelines and standards to ensure that industrial plants operate as good
acoustical neighbors (Wood, 2005).4 Uncertainty caused by the lack of well-defined, quantitative standards is a significant issue for companies planning and submitting plans for new industrial facilities. Significant delays caused by poorly defined standards have affected the construction of oil refineries, wind power farms, clean coal facilities, and nuclear power plants. Standards should set criteria and guidelines for low-frequency noise, tonal noise, and intermittent noise coming from, and within, new facilities; should define how equivalent noise levels should be used; and should establish protocols for documenting predevelopment, baseline, ambient noise levels in the surrounding environment.
New noise guidelines are needed for electricity-generating and transformer facilities and other industrial structures. Databases of industrial noise, similar to existing databases for cars, trucks, and airplanes, are needed to document industrial sound power and sound radiation, mufflers, building elements, and barriers, among other building characteristics. New noise modeling programs are also badly needed, as are improvements in noise control technologies (e.g., large axial fans) to reduce operating noise and more rapid technology transfer from government research programs to industry.
WIND TURBINE NOISE
Growing interest in renewable energy sources has led to the design and installation of large modern wind turbines for electric power generation. European nations such as Germany, Denmark, and Spain have developed wind power generation, and there is concern in Europe about the noise generated by these machines—as there is in the United States. Three conferences on wind turbine noise have been held in Europe, and a fourth is scheduled for 2011 (WTN2005, WTN2007, WTN2009, WTN2011).
There have been reports of adverse effects of noise in the United States, particularly downwind of turbines close to communities. Low-level audible noise is generated and sometimes modulates at the blade passage frequency of the turbines. Today’s large modern wind turbines with blades rotating upwind of the tower are quieter than earlier wind turbines with blades that rotated through the turbulent wake downwind of the tower.
One concern is the adequacy of A-frequency weighting as a metric to assess the effect of noise on people. Another is the fact that these turbines are sometimes located in remote areas or quiet communities where the background noise level in the absence of ground-level wind can be very low. Thus, wind turbine noise is sometimes audible above the background at sound pressure levels that in most cases would be considered to have a minimal effect on people. A variety of state and local noise regulations have been developed to address concerns about noise from wind turbines (Bastasch, 2009; Barnes, 2007). Wind turbine research is ongoing at the National Renewable Energy Laboratory of the U.S. Department of Energy. The report Wind Turbine Sound and Health Effects—An Expert Panel Review, prepared by a panel of scientific and medical professionals from several countries, provides an assessment of plausible biological effects of exposure to wind turbine sound (Colby et al., 2009). There is also a short discussion of wind turbine noise in a National Research Council report (NRC, 2007).
NOISE IN BUILDINGS
There are many sources of noise in buildings—including noise from outside such as the transportation noise sources described above; noise from heating, ventilating, and air-conditioning systems; noise generated by equipment used by occupants, and noise generated by the occupants themselves. The section “Noise Control in Buildings” in Chapter 5describes current problems and future challenges. The issues include noise in homes, noise in hospitals, and noise in business environments. There is widespread dissatisfaction with noise in buildings in which business is conducted. Postoccupancy evaluations by the Center for the Built Environment at the University of California at Berkeley (2007) indicate that occupants are generally dissatisfied with noise and sound privacy. It has also been shown that the move to design “green” buildings can further degrade the acoustical environment (Muehleisen, 2009; Razavi, 2009). Issues include windows that open, low-height screens, natural ventilation systems, and lack of “green” sound absorptive materials. Noise in hospitals and other buildings is covered in Chapter 5.
NOISE FROM CONSUMER PRODUCTS
Noise from consumer products can be a nuisance in the home, but it can be more than a nuisance when noisy products, such as lawnmowers and leaf blowers, are operated in suburban and urban environments. Reducing product noise is a significant factor in the market success of many consumer products. In addition, some foreign suppliers have made significant inroads in U.S. markets by making less noise a distinguishing feature of their products. Some U.S. manufacturers have also begun to take product sound seriously, but cost constraints frequently make it difficult for them to add engineering modifications to produce quieter products.
For some products, such as automobiles, sound is very important, and companies spend heavily to make their cars quiet and pleasant. Automobile companies have large staffs and good facilities for sound research and development, but most appliance/consumer products companies do not. One
reason for this is that appliances, health care, and personal care products are subject to much more frequent changes than cars, and consumers regularly replace older products or choose to buy new ones because of a desired feature. The effect of frequent changes has been to compress development schedules and limit the transfer of improved noise suppression (e.g., a quieter way to support a small motor) to new models.
Community and building noise is too broad a topic to be described in a single chapter. Nevertheless, a few examples can be given, organized according to the source of noise—and that is the approach used in this chapter.
Noise around the nation’s airports has received a great deal of attention; still, many problems remain to be solved. Noise barriers have been the solution of choice at many locations along the nation’s highways, but (as will be seen in later chapters) progress is being made to reduce the noise generated by the interaction between tires and the road surface.
Environmental, construction, and building noise is an increasingly widespread problem in densely populated urban areas, and the situation in New York City exemplifies that. As the rail network expands in the United States, rail noise will become more of an issue than it is today.
Finally, noise in quiet areas such as national parks is part of the community noise issue—broadly defined—and is introduced here and emphasized in the following sections of this report.
Barnes. J.D. 2007. A Variety of Wind Turbine Noise Regulations in the United States—2007. Proceedings of the Second International Meeting on Wind Turbine Noise, Lyon, France, September 20–21.
Bastasch, M. 2009. Oregon’s Wind Turbine Noise Regulations. Proceedings of the Third International Meeting on Wind Turbine Noise, Aalborg, Denmark, June 17–19.
Bronzaft, A., and G. Van Ryzin. 2004. Neighborhood Noise and Its Consequences: A Survey in Collaboration with the Council on the Environment of New York City. Special Report #4. New York: Council on the Environment. Available online at http://www.cenyc.org/files/cenyc/noisesurvey04.pdf.
Bronzaft, A., and G. Van Ryzin. 2006. Neighborhood Noise and Its Consequences: A Survey in Collaboration with the Council on the Environment of New York City. Special Report #9. New York: Council on the Environment. Available online at http://www.cenyc.org/files/cenyc/noisesurvey06.pdf.
Bronzaft, A., and G. Van Ryzin. 2007. Neighborhood Noise and Its Consequences: Implications for Tracking Effectiveness of the NYC Revised Noise Code. Special Report #14. New York: Council on the Environment. Available online at http://www.noiseoff.org/media/cenyc.noise.report.14.pdf.
Center for the Built Environment, University of California at Berkeley (2007). Acoustical Analysis in Office Environments Using POE (Post Occupancy Evaluation) Surveys. Available online at http://www.cbe.berkeley.edu/research/acoustic_poe.htm.
CENYC (Council on the Environment of New York City). 2009. Noise. Available online at http://www.cenyc.org/greenlife/noise.
Colby, W.D. 2009. Wind Turbine Sound and Health Effects—An Expert Panel Review. American Wind Energy Association and the Canadian Wind Energy Association. Available online at http://www.awea.org/newsroom/releases/AWEA_CanWEA_SoundWhitePaper_12-11-09.pdf.
Corbisier, C. 2003. Living with noise. Public Roads 67(1). Available online at http://www.tfhrc.gov/pubrds/03jul/06.htm.
Denver Post. 1997. Residents sue Denver Airport and Adams County over noise. June 7.
Denver Post. 2005. Homes jump DIA noise boundary. April 8.
Denver Post. 2006. Denver airport partnership prepares guides for new homebuyers. April 17.
DOI (U.S. Department of the Interior). 1995. Report on Effects of Aircraft Overflights on the National Park System. Washington, DC: National Park Service. Available online at www.nonoise.org/library/npreport/intro.htm.
EPA (U.S. Environmental Protection Agency). 1974. Information on Levels of Environmental Noise Requisite to Protect Public Health and Welfare with an Adequate Margin of Safety. EPA Report 550/9-74-004. Washington, DC: Office of Noise Abatement and Control. Available online at www.nonoise.org/library/levels74/levels74.htm.
FAA (Federal Aviation Administration). 2004. Aviation and the Environment. Available online at http://www.faa.gov/library/reports/media/congrept_aviation_envirn.pdf.
FHWA (Federal Highway Administration). 2006. Construction Noise Handbook. Available online at http://www.fhwa.dot.gov/environment/noise/handbook/index.htm.
FHWA (Federal Highway Administration). 2009. Summary of Noise Barriers Constructed by December 31, 2004. Available online at http://www.fhwa.dot.gov/environment/noise/barrier/sintro.htm.
Miller, N.P. 1999. Mitigating the Effects of Military Aircraft Overflights on Recreational Users of Parks. AFRL-HE-WP-TR-2000-0034.
Miller, N.P. 2003. Transportation noise and recreational lands. Noise/News International 11(1):9–21. Available online at http://www.noisenewsinternational.net/docs/miller-2003.pdf.
Miller, N.P. 2008. U.S. national parks and management of park soundscapes: A review. Applied Acoustics 69(2):77–92.
Muehleisen, R.T. 2009. Noise Problems and Opportunities in “Green Buildings.” Presentation at the Second CAETS Forum on Worldwide Noise Sources, Ottawa, Canada, August 25, 2009. Available online at http://www.noisenewsinternational.net/docs/caets-2009.
NCEJ (Noise Control Engineering Journal). 1999. 47 (3–4), Special Issues.
NPS (National Park Service). 2009. Sources of Human-Caused Sounds in National Parks. Available online at http://www.nature.nps.gov/naturalsounds/sources/.
NRC (National Research Council). 2007. Environmental Impact of Wind Turbine Noise. Washington, DC: National Academies Press. Available online at http://books.nap.edu/openbook.php?record_id=11935&page=160.
Razavi, Z. 2009. Acoustical Improvements with Natural Air Ventilations in the Liu Institute at the University of British Columbia. Proceedings of INTER-NOISE 2009. The 2009 International Congress on Noise Control Engineering, Ottawa, Canada, August 23–26 Available online at http://www.bookmasters.com/marktplc/00726.htm.
Schomer, P.D. 2009. Visitor perception of park soundscapes: A research plan. Noise/News International 17(2):51–56. Available online at http://www.noisenewsinternational.net.
Schomer, P.D., G.F. Stanley, and W. Chang. 2008. Visitor Perception of Park Soundscapes: A Research Plan. Proceedings of INTER-NOISE 08, The 2008 International Congress and Exposition on Noise Control Engineering, Shanghai, China, October 26–29. Available online at http://www.internoise2008.org/ProceedingsforSale.htm or http://scitation.aip.org/journals/doc/INCEDL-home/cp/.
Sutherland, L.C. 1999. Natural quiet: An endangered environment. How to measure, evaluate, and preserve it. Noise Control Engineering Journal 47(3):82–86.
Thalheimer, E., and C. Shamoon. 2007. New York City’s new and improved construction noise regulation. Proceedings of NOISE-CON 07. The 2007 National Conference on Noise Control Engineering, Reno, Nevada, October 22–24. Available online at http://www.bookmasters.com/marktplc/00726.htm.
Thalheimer, E. 2000. Construction noise control program and mitigation strategy at the Central Artery/Tunnel Project. Noise Control Engineering Journal 48(5):157–165.
Thalheimer, E. 2001. Proactive Construction Noise Control Policies Developed for the Central Artery/Tunnel Projects. Proceedings of NOISE-CON 01, The 2001 National Conference on Noise ControlEngineering, Portland, Maine, October 29–31. Available online at http://www.bookmasters.com/marktplc/00726.htm.
WTN2005. First International Conference on Wind Turbine Noise, Berlin, Germany, October 17, 18. Available online at http://www.confweb.org/wtn2005.
WTN2007. Second International Conference on Wind Turbine Noise, Lyon, France, September 20–21. Available online at http://www.confweb.org/wtn2007.
WTN2009. Third International Conference on Wind Turbine Noise, Aalborg, Denmark, June 17–19. Available online at http://www.confweb.org/wtn2009.
WTN2011. Wind Turbine Noise 2011, Rome, Italy, April 12–14, 2011. Announcement online at http://www.windturbinenoise2011.org.