Airport Noise Grants: FAA Needs to Better Ensure Project Eligibility and Improve Strategic Goal and Performance Measures
Published: 2012-09-12T00:00:00

Fast Facts:

Highlights:
section_title: Why GAO Did This Study
paragraphs: The Federal Aviation Administration (FAA) predicts that air traffic in the United States will increase 20 percent by 2024. If not mitigated, the noise associated with these flights could significantly diminish the quality of life for communities surrounding airports and constrain an airports ability to expand. Over the last 30 years, Congress has provided billions of dollars in grants under the Airport Improvement Program to airports to reduce and mitigate significant noise exposure. FAAs overall strategic noise goal is to reduce the population exposed to significant noise to fewer than 300,000 people nationwide.
At your request, GAO (1) described how airport noise exposure has changed, (2) evaluated noise grant results, and (3) assessed potential future demand for these grants. GAO analyzed FAA data on noise grants, planned projects, and population exposure and reviewed relevant literature. GAO also conducted interviews with relevant airport and FAA officials and industry representatives, as well as visited seven airports that have used noise grants, judgmentally selected based on size, location, and other factors.
section_title: What GAO Found
paragraphs: The number of people in the United States exposed to significant airport noise has steadily declined from roughly 7 million people in 1975 to about 309,000 today. This change reflects large decreases in the size of areas that are exposed to significant airport noise and is primarily due to improvements in aircraft technology.
Since 1982, FAA has provided $5.8 billion in Airport Improvement Program noise grants to 481 airports for residential and public building noise insulation and land acquisition, among other project types. The majority of grants went to airports that voluntarily undertook Noise Compatibility Programs (NCP). While these funds benefitted thousands of people, GAO identified two areas of concern regarding FAAs enforcement of project eligibility criteria that creates a risk that some undetermined amount of grant funds may have gone to projects that do not meet FAAs project eligibility criteria. First, FAA does not always require airports to maintain updated and accurate noise exposure maps to define eligible project areas. For example, half of the noise exposure mapswhich show the areas around an airport that are exposed to significant airport noise and are a key element in determining project eligibilityare from the 1990s or earlier. For an airport to receive a noise grant, program criteria generally require that such maps are updated every 5 years, but nine airports received $87.6 million in grants in fiscal years 2010 to 2011 based on maps that predate 2000. Second, FAA has inconsistently implemented requirements that limit residential noise insulation projects to homes with interior noise levels above an established threshold. In the absence of FAA enforcement, airports have little incentive to update maps and limit residential treatment because doing so might eliminate planned projects expected by the public. Concurrent to GAOs review, FAA issued new guidance that should substantially address this risk if effectively implemented. Further, the results of noise grants are not linked to FAAs strategic noise reduction goal and measurement approach. For example, the goal does not include the results of noise insulation of homes and schools. As a result, there is insufficient performance information about the effects of noise grants and the extent to which noise exposure remains a constraint on airport growth.
There has been an increase in the estimated cost of planned noise mitigation projects in FAAs 2011 National Plan of Integrated Airport Systems report to Congress, but a number of indicators point to a future decline in demand for grants for noise projects. Specifically, the 2011 report, compared to prior reports, includes a smaller portion of projects in the most significantly noise-impacted areas. Further, since the 2001 report, the number of airports planning eligible noise projects is down 16 percent, with about half the number of planned projects. Additionally, fewer airports are developing new noise compatibility programs and many of the 234 airports with such programs may be completed. For example, 102 of 137 airports with an NCP more than 10 years old received no noise grants since 2007, an indication that those airports may have completed all eligible projects in those plans. Finally, about a third of the people living in significantly noise-impacted areas reside near airports that have not completed, and may never complete, an NCP, a necessary step before an airport can use noise grants for residential noise insulation. This population, therefore, may never be reached by FAAs grant program.
section_title: What GAO Recommends
paragraphs: GAO recommends that the Department of Transportation align its strategic goal for noise reduction with the results of the noise grant program and establish corresponding performance measures. The department provided technical comments and agreed to consider the recommendations.

section_title: Letter
paragraphs: The number of commercial and general aviation flights in the United  States is estimated to increase 20 percent by 2024, according to the  Federal Aviation Administration (FAA). While airports provide access to  transportation for millions of people each day, airport noise—by, for  example, interfering with speech, sleep, and student learning—can  severely diminish quality of life in communities around airports and spur  community objections to airport operations and continued growth. Since  1982, to address and mitigate the problems associated with airport noise,  Congress has provided a dedicated source of funding within the Airport  Improvement Program (AIP) for noise mitigation projects. FAA  administers the AIP, which has provided nearly $5.8 billion in grants since  fiscal year 1982 to sound insulate homes and other buildings near  airports as well as acquire land in, and relocate residents away from,  significantly noise impacted areas, among other noise mitigation   FAA’s 2018 strategic goal for noise is to reduce the residential  activities.population exposed to significant airport noise in the United States to less  than 300,000 people. AIP-funded noise mitigation projects, administered  by airports, are FAA’s primary tool to achieve this goal.
FAA has an ongoing responsibility to balance the growing demand for  aviation capacity against the environmental concerns and effects on  communities caused by airport noise. Aircraft technology, the number of  aircraft operations, and noise levels have changed markedly since FAA  first began providing AIP noise grants. Moreover, the implementation of  the Next Generation Air Transportation System (NextGen)growth in aircraft operations that NextGen investments could spur may  lead to new demand for airport noise mitigation or new noise challenges.  As a result, it is not clear how well the AIP noise grant program will be  able to provide an appropriate and effective tool for addressing changes  in future airport noise exposure. In light of these concerns, you requested  that we examine FAA’s AIP noise grants. Our report addresses the  following questions:  1.  How has overall airport noise exposure changed since AIP noise  grants were first funded? 2.  How have AIP noise grants been used by airports to mitigate noise  and what have these grants achieved? 3.  What is the likely future demand for AIP noise grants?
To describe how airport noise exposure has changed over time, we  reviewed available literature; assessed the use of FAA noise models;  interviewed industry, FAA, and airport officials; and, for illustrative  purposes, performed Geographic Information System (GIS) analysis of  changes in the areas exposed to airport noise near several large airports.  To assess how AIP grants have been used by airports for noise mitigation  projects and planning, we analyzed FAA data in the System of Airport  Reporting (SOAR). This database includes detailed information about AIP  grantees, Passenger Facility Charge (PFC) approvals, project types, and  other information. We performed a data reliability assessment of SOAR  that included electronic testing, review of FAA documentation, and  interviews with relevant FAA officials. We found the data to be sufficiently  reliable for our purposes. To assess the likely future demand for AIP  noise grants we compiled and analyzed a range of data from different  sources. Sources included planned projects in the National Plan of   FAA’s main planning tool for  Integrated Airport Systems (NPIAS),identifying future airport capital projects; data on airports’ Noise  Compatibility Programs (NCPs) and noise exposure maps, both key  documents for many AIP noise grants; and FAA’s estimates of the  population exposed to significant airport noise. FAA calculates these  estimates with models that are broadly used and generally considered  accurate for the purposes intended. We did not independently assess  FAA’s models. To illustrate the results of our analysis and better  understand the real world implementation and future of airport noise  programs, we reviewed noise programs at seven judgmentally selected  airports. These airports were selected to represent a range of sizes,  geographical locations, and use of noise grants. Information gathered  from these reviews is not generalizable to all airports. We conducted this  performance audit from October 2011 to September 2012 in accordance  with generally accepted government auditing standards. Those standards  require that we plan and perform the audit to obtain sufficient, appropriate  evidence to provide a reasonable basis for our findings and conclusions  based on our audit objectives. We believe that the evidence obtained  provides a reasonable basis for our findings and conclusions based on  our audit objectives.
subsections: section_title: Background
paragraphs: Since the late 1950s, noise from aircraft and other airport operations has  generated controversy within many surrounding communities and can be  a constraint on airport development and aircraft operations. As we have  previously reported, noise is one of the top environmental concerns at  airports.such as cities, counties, or port authorities, which have primary  responsibility for addressing community concerns about noise. The  federal government has a long history of helping airports address noise  concerns by, for example, defining how airport noise is measured;  providing a framework for assessing the impact of noise and for airports  to plan noise mitigation projects; and funding eligible noise mitigation  projects. Within this context, airports may undertake a range of noise  mitigation projects. The federal government has also required the use of   Most airports are owned and operated by public authorities,  quieter aircraft technologies. The Aviation Noise and Capacity Act of 1990  required that all commercial jets at civilian airports switch to Stage-3  aircraft by the year 2000. Airlines phased out the loudest aircraft over  time, and by 2000, the U.S. commercial fleet was composed of quieter  aircraft than in the 1990s.
Pub. L. No. 96-193, §104, 94 Stat. 51 (1980). incompatible land uses and estimates of the population residing within  those contours), and the location of noise sensitive public buildings, such  as schools, as defined by FAA regulations. For example, residential  development within the DNL 65+ dB contour is deemed incompatible,  whereas commercial and manufacturing development is not because of  the different impacts of noise on people. The NCP documents the noise  mitigation projects the airport proposes to implement and is submitted to  FAA for review and approval. The airport may offer mitigation measures  within incompatible land use areas that meet other eligibility criteria. For  example, a residence located within a DNL 65+ dB area that also has  interior noise levels above DNL 45 dB may receive noise insulation.  Airport participation in the Part 150 process is voluntary. The typical level  of noise in a suburban residential neighborhood that is not near an airport  is about DNL 50 dB and an urban residential area is about DNL 60 dB.
FAA administers two programs that fund airports’ capital development  projects, including noise-related projects. With the creation of the AIP in  1982, FAA had a source of funds to provide grants to airports for noise  mitigation projects. Congress reserved a set-aside specifically for noise  projects that is currently funded at no more than $300 million per year, but  has also expanded over time to include other types of environmental  projects including water projects at airports undertaken as a result of an  environmental record of decision for an airport development project and  certain types of air quality projects. Capital projects in approved NCPs  that meet AIP criteria are eligible for AIP grants. Further, airports can be  awarded AIP noise grants for some types of noise mitigation projects  without an NCP. First, in 2003, AIP noise grant eligibility was temporarily  expanded by permitting FAA to provide grants to state and local  governments for land use compatibility planning and noise mitigation  projects around large and medium hub airports if the airport had not  submitted a Part 150 study or had not updated its NCP for more than 10   Second, the National Environmental Policy Act of 1969 (NEPA),  years.as amended, requires federal agencies to examine the potential impacts  associated with a proposed federal action, including potential noise  impacts. As a result, airport development proposals, such as adding new  runways or otherwise expanding capacity, must be reviewed for the  potential environmental effects as fully as technical, economic and other  considerations. Likewise, operational changes, such as changes in flight  paths, may trigger a similar review process, depending on the extent of  the likely noise impact. These reviews may require airports to prepare an  environmental assessment or may require the FAA to prepare an  environmental impact statement which could, in turn, lead to a noise  mitigation project that is eligible for AIP funding. Airports must match AIP  grants to varying degrees, depending on an airport’s size. The second  FAA funding program for noise mitigation projects is the Passenger  Facility Charge (PFC) program. This program allows publicly operated  airports to charge passengers a fee and retain these fees for their use on  FAA-approved projects, including those that reduce noise. Project  eligibility criteria for the PFC and AIP programs are largely the same,  although an NCP is not required to use PFC funds for noise mitigation  projects. PFC funds can be used to match AIP grants.
There are a variety of projects and actions to mitigate and reduce airport  noise that airports may use, some of which are eligible for AIP grants.  See figure 1.
section_title: Populations Exposed to Significant Airport Noise Have Declined Because of Improvements in Aircraft Technology
paragraphs: The number of people exposed to airport noise has been steadily  declining for several decades, according to FAA. FAA uses a model,  called Model for Assessing Global Exposure from Noise of Transport  Airplanes (MAGENTA), to calculate a high-level national estimate of the  population exposed to different levels of airport noise. MAGENTA uses,  among other factors, airport-level information about the number of aircraft  operations, types of aircraft, flight paths, and census data for communities  near airports (see sidebar). Individual airports may have, through Part  150 studies or through studies undertaken for NEPA compliance, for  example, more precise estimates. FAA estimates that approximately 7  million people lived in areas exposed to significant airport noise—DNL 65  dB or higher—in 1975. Through the 1980s and 1990s, this exposure  declined to less than a million by the year 2000. FAA estimates that about  309,000 people currently live in areas at or above DNL 65 dB. FAA  estimates also show declines in the populations exposed to non- significant airport noise (i.e., below DNL 65 dB). For example, FAA  estimates that between 2000 and 2010 the number of people residing in  areas with DNL 60 to 65 dB decreased from about 3 million to 1.5 million  (see fig. 2). The downward trend in noise exposure has held relatively  steady despite overall increases in air traffic. For example, total U.S.  operations—including arrivals and departures—went up from  approximately 17.4 million in 2000 to 20.8 million in 2011, though some  locations have seen declines.
FAA’s model is intended to determine the population living within  geographic areas exposed to airport noise, regardless of whether the  houses or apartments have been sound insulated using AIP, PFC, or  other funds. Consequently, some percentage of the population that FAA  estimates is exposed to DNL 65 dB or higher lives in structures that have  benefited from noise insulation. There are no readily available data to  determine this percentage. Thus, FAA’s model cannot be used to  specifically assess the results of AIP grants.
As with the shrinkage in the populations living in noise-exposed areas,  the geographic areas exposed to significant noise around airports have  also generally been shrinking based on multiple recent assessments of  DNL 65 dB noise contours that we, FAA officials, and others have  conducted. Likewise, FAA and airport officials, as well as industry  representatives with whom we spoke generally agreed that the DNL 65  dB noise contours around airports have been shrinking. We did not  perform an overall assessment of the extent of this change because noise  exposure maps are updated at different times at the discretion of  individual airports. At all seven of the airports we examined—including  two airports that have recently added runways—noise contours have  shrunk overall, according to airport officials or our assessments of noise  exposure maps for these airports. For example, at Atlanta-Hartsfield  airport, the DNL 65 dB contour has become smaller since the 1980s  despite a tripling of airport operations. Likewise, at Seattle-Tacoma  International airport, noise contours are substantially smaller today than in  the past. Specifically, the DNL 65 dB contour decreased in area almost  60 percent, from approximately 14 to 6 square miles, from 1998 to 2009.  However, while noise exposed areas have generally become smaller  overall, the shapes of some contours may have changed or shifted over  time, decreasing significant noise exposure in some areas, but also  exposing new areas to significant noise. For example, while the DNL 65  dB area around Los Angeles International airport decreased from  approximately 13 to 11 square miles in total area from 1987 to 2011, the  shape of the contour changed and now includes different communities  (see fig. 3).
Improvements in aircraft technology, spurred by federal mandates and  industry actions to reduce aircraft noise levels, have been the largest  contributor to the shrinkage in airport-noise-exposed populations and  noise contours. FAA and airport officials we spoke with generally agreed  that the phase out of the loudest aircraft—specifically, stage 1 and stage  2 aircraft weighing over 75,000 pounds—by 2000 and improved aircraft  and engine technology are the most significant factors causing noise  contours to shrink. For example, reduced air velocity moving through  improved engines has reduced engine noise. Likewise, acoustical liners  and improved air flap designs have reduced airframe noise.factors that may have contributed to decreased airport noise exposure  include the implementation of flight procedures that can, for example,  direct air traffic over less populated areas during arrivals and departures.
section_title: FAA Is Taking Steps to Ensure that Projects Meet Eligibility Criteria, and FAA’s Strategic Noise Goal Is Not Linked to the Noise Grant Program
paragraphs: AIP noise grants have been widely used by airports and have provided  noise mitigation to thousands of people. However, in recent years, the  program has benefited fewer people and FAA has not met its program  goals. In light of the shrinking airport noise contours discussed above,  FAA’s enforcement of grant eligibility criteria—related to noise exposure  maps and the assessment of interior residential noise—creates a risk that  some noise grants may not have met eligibility criteria, especially in the  edges of the noise contour where noise may be below DNL 65 dB. FAA  has recently issued guidance to address these areas of grant eligibility  criteria, which if followed should reduce the risk of making ineligible  grants. In addition, FAA’s overall strategic goal for its noise-related  activities is not linked to the results of noise grant investments.
subsections: section_title: Grants Are Widely Used for Noise Insulation Projects and Land Acquisition
paragraphs: Since fiscal year 1982, FAA has provided about $5.8 billion in AIP noise  grants to 481 commercial and general aviation airports, reflecting broad  participation in the program by airports through the program’s history.  Specifically, most primary airports have been awarded at least one noise  grant. General aviation airports have received $75 million in grants since  fiscal year 1982. Airports that have completed voluntary Part 150 studies  and have had an NCP approved by FAA have received the majority of  AIP noise grant funding. As of May 2012, 234 airports had an approved  NCP and received grants totaling about $5 billion. Primary commercial  airports account for 168 of the 234 approved plans. Of the remaining 66,  62 are larger general aviation or reliever airports. Additionally, grants  have been awarded to airports and communities outside the Part 150  framework following statutory changes in 2003 that allow for such  grants. During fiscal years 2005 through 2011, grants totaling $336  million have been awarded to 24 airports or communities that do not have  NCPs. These grants went to some of the largest airports in the country.  For example, the Port Authority of New York and New Jersey secured  $134 million in grants for noise insulation of public buildings—mostly  schools—near Teterboro, Newark, LaGuardia, and Kennedy airports.
AIP noise grants have funded a range of different types of projects,  reflecting FAA and airport priorities, with noise insulation and land  acquisitions receiving the most support. From fiscal year 2000 through  2011, out of approximately $3.2 billion total, residential and public building  noise insulation projects received approximately $1.7 billion and $456  million, respectively; property acquisition projects received $780 million  (see fig. 4). In addition, since fiscal year 2000, FAA has approved PFC  applications from 73 airports to collect nearly $2 billion for noise mitigation  projects.
The distribution of funds reflects airport priorities and FAA’s project  assessments based on AIP grant-scoring formulas as well as judgmental  considerations. FAA’s grant scoring formula ranks proposed projects in  higher DNL areas above lower DNL areas and at larger airports above  smaller airports. For example, a proposed residential noise insulation  project in the DNL 70-74 dB range would score higher than a project in  the DNL 65-69 dB range, regardless of airport hub size. In addition to  formula scores, FAA made grant award decisions based on judgmental  factors such as input from regional FAA officials—such as FAA’s Airports  division regional offices or Airports District Offices (ADO)—about an  individual airport’s capacity to execute its proposals and consideration of  FAA regional priorities, as well as to meet national priorities. In recent  years, FAA has also considered information on the number of expected  beneficiaries—whether residents, students, or other groups—and  attempted to fund a mix of grants that will meet an annual beneficiary  goal. These beneficiary goals, discussed later in this report, are  measured in the number of people expected to benefit from awarded  grants. The fiscal year 2012 goal was 15,000 people.
In the first decades of the program, noise grants largely went to projects  in areas most significantly impacted by airport noise—generally areas  closest to airports—while grants in more recent years have gone to  projects in areas that are less significantly impacted, but still deemed to  be exposed to DNL 65 dB or higher noise levels (see fig. 5). For example,  based on FAA data, all 385 acquisition and noise insulation grants from  fiscal year 1982 through 1991 went to projects in DNL 75 dB or higher  areas. In the last 12 years, as areas of higher noise exposure were  increasingly already addressed, a large majority of grants went to projects  in DNL 65-69 dB areas, the lowest significant noise-level eligible for  grants under the program. Also, most of the grants for planning activities  were awarded in the first half of the program’s history. Specifically,  through fiscal year 2000, FAA awarded 332 planning grants for  approximately $50.3 million. As of 2000, 195 airports had approved  NCPs. Since fiscal year 2000, FAA has awarded 117 grants totaling  approximately $45.5 million for planning. Since 2001, thirty-nine airports  had new NCPs approved by FAA. In some cases, instead of conducting a  Part 150 noise study, airports completed environmental impact  statements for major proposed development that included developing  noise exposure maps that could be used to identify mitigation projects  eligible for AIP noise grants.
Consistent with the grant trends discussed above, according to FAA and  airport officials with whom we spoke, planned projects within individual  airport noise programs were prioritized to first address the most noise  impacted areas or specific project types. At all of the seven airports we  visited, officials indicated that they began mitigation efforts with properties  in the noisiest areas that are typically closest to the airport or with  schools. For example, Burbank (Bob Hope) Airport in California first  insulated most of the schools inside the DNL 65 dB contour before  beginning residential noise insulation. At Boeing Field in Seattle,  residences in areas above DNL 70 dB were generally insulated first.  However, airport officials also noted that project selection can also  depend on practical program considerations, not simply noise exposure.  For example, before starting a residential insulation project, the airport  sponsor must identify and sign up homeowners and complete other  planning steps—all of which take time—and could lead to noise insulation  of homes in areas with lower noise before homes in higher noise areas  simply because they cleared these steps more quickly.
As part of managing the grant program, FAA sets beneficiary goals for  AIP noise grants and tracks progress towards those goals. Beneficiary  data, assessed annually, are used as part of FAA’s annual budget  justification to Congress. These data aggregate the number of people  who have been—or are expected to be—relocated following acquisitions,  as well as residential and student population soundproofing beneficiaries  as a result of the grants awarded that year. Based on this information,  noise grants have helped reduce or mitigate airport noise exposure for   However, as shown in figure 6, in recent years,  thousands of people.fewer beneficiaries have been reached by these grants, FAA has fallen  short of its beneficiary goals, and results have come at a higher per  beneficiary cost. For example, in fiscal year 2011, the awarded noise  grants benefited 10,913 people, short of the goal of 15,000, at nearly 40  percent higher per beneficiary costs than in fiscal year 2005. FAA officials  explained that these trends are partly attributable to increasing  construction costs due to inflation and more projects in higher cost areas,  such as San Diego and Los Angeles. Finally, as discussed more below,  these results are not reflected in FAA’s overall reporting on the population  exposed to significant airport noise.
AIP noise grants have been the most important source of funding for  noise mitigation projects, but other funding sources have also been used.  Officials representing all seven of the airports we reviewed agreed that  AIP funds were of great importance to their noise mitigation programs and  most stated that, in the absence of these funds, much less, if anything,  would likely have been spent on such projects. For example, Boeing Field  does not collect PFCs, and according to airport officials, its noise  mitigation program is highly dependent on AIP funds. However, many  airports do have other funding sources—primarily PFC funds—that can  be used for noise mitigation projects. According to FAA and airport  officials, PFC funds are most commonly used to provide the local  matching funds required of AIP grantees. For example, officials at five of  the six airports that we reviewed that collect PFCs indicated that PFCs  were used for noise mitigation projects as a match to AIP grants. PFCs  also have been used to supplement AIP funds. FAA officials indicated  that PFC funds may be used to speed up the completion of planned noise  mitigation projects in light of limited availability of AIP grants. However,  most officials agreed that projects essential to the continued operations of  the airport, such as runway rehabilitation and maintenance, were typically  a higher priority for PFCs than noise mitigation projects. FAA’s existing  data system does not distinguish between projects that are fully funded  using PFCs from those where PFCs are used to match AIP grants or  provide supplemental funding.
section_title: Outdated Noise Exposure Maps and Inconsistent Application of Interior Noise Standards Increase Risks for Noise Grant Funds
paragraphs: We found that many of the FAA-accepted maps used to determine project  eligibility for noise grants are outdated and could overstate the actual size  of the DNL 65+ dB areas around airports, putting some federal grant  investments at risk of funding projects that do not meet the eligibility  criteria. Following the passage of the Vision 100 Act in 2003, airports  have been required to update noise exposure maps when a change in  airport operations would indicate that the maps on file with FAA no longer  accurately show the size or shape of the airport’s DNL 65 dB noise  contours and relationship to land uses. Federal regulation defines a  significant change as a 1.5 decibel increase or decrease in the DNL for a  substantial land area exposed to airport noise. Additionally, if the maps on  file with FAA are older than 5 years, then the airport must certify that the  maps continue to accurately reflect current conditions.explained that maps over 5 years old should be periodically reviewed for  potential inaccuracies or changed conditions. In light of the general  shrinkage in DNL 65 dB contours, some of the FAA-accepted maps are  outdated and therefore could be inaccurate:
Most maps that could be used for noise grant eligibility are more than  5 years old. According to FAA data, of the 252 airports that have  developed noise exposure maps accepted by FAA, 189 maps are  more than 5 years old.from 1999 or before, predating the phase-out of stage 2 commercial  aircraft by the year 2000. To the extent that the contours depicted by  these maps reflect conditions from when these louder aircraft  operated, the actual noise exposed area today is likely smaller.
Further, we found 126 airports with maps
Many airports with old maps continue to be awarded noise grants for  residential noise insulation in DNL 65-69 dB designated areas—the  area that would first drop out of grant eligibility because of shrinking  noise contours. Of the 28 airports that were awarded noise grants for  this purpose in 2010 or 2011, 10 have maps from 2000 to 2005. In  addition, nine of the 126 airports with maps from 1999 or before  received a total of $87.6 million in grants in fiscal years 2010 and  2011 for residential insulation projects in the DNL 65-69 dB area of  the official map.
Some airports have produced separate noise maps for reasons  unrelated to Part 150 noise compatibility planning, such as to meet  state requirements or for environmental reviews. In some cases,  these maps indicate that noise-exposed areas have decreased, but  FAA has not required the airport to update the map used for AIP  eligibility. For example, Ontario International’s noise mitigation  program area is currently defined by a map from 1990, but to meet  state noise requirements, the airport produces quarterly noise  exposure maps. While the technical details of the FAA-accepted map  and these quarterly maps differ, preventing exact comparisons, the  area exposed to significant noise in the more recent maps covers very  little residential land across a much smaller area than in the 1990  map.year 2007 and has identified $58.4 million in planned AIP-funded  noise mitigation projects for fiscal years 2013 through 2017.
The program has received $25.8 million in grants since fiscal  These indicators suggest that some risk of funding projects that do not  meet eligibility criteria exists. Without current and accurate noise maps, or  documentation of an alternative project justification, such as  environmental agreements, there is no readily available way to determine  how many, if any, FAA-funded projects did not meet the requirement of  being inside the DNL 65 dB contour at the time of funding, though FAA  officials believe that few, if any, grants have funded projects to date that  do not meet the eligibility criteria.
We did not assess the extent that FAA officials in other districts consulted additional  information in similar circumstances nor did we evaluate FAA’s review of individual grant  requests. known to be inaccurate to be used in an effort to continue funding an  existing airport’s noise mitigation program. Several airport officials  acknowledged that the maps used in their AIP funded noise program  could overstate current exposure. Some airport officials we spoke with  explained that they were reluctant to update maps when doing so could  limit AIP eligibility for planned projects that the airport has already  promised residents. Airport and FAA officials explained that planned  project areas, as reflected in noise maps, need to be somewhat stable.  They emphasized that while noise exposure is constantly evolving, it  takes time to define a program, receive a grant, enroll people, and then  design and execute projects. According to these officials, planned  projects represent promises to communities, making program stability  important. Changing or canceling planned projects because of decreasing  noise can create public relations problems for airports, especially since  gradual decreases in DNL may be difficult for residents to perceive. In  light of these considerations, airport sponsors are unlikely to limit projects  to only those that clearly meet program criteria without FAA’s insistence.  FAA, however, is responsible as the steward of the program for insuring  that AIP noise mitigation funds only support projects that meet the  program’s eligibility criteria. Because the program has limited funding,  paying for noise mitigation that is no longer needed takes money away  from eligible projects that did not receive funding or from other aviation  priorities.
Furthermore, program criteria—including regulations and FAA guidance— require that only homes located in DNL 65 dB areas with interior noise  levels above DNL 45 dB can be approved for noise treatment, with limited  exceptions, such as neighborhood equity. For example, FAA’s principal  guidance on AIP implementation explains that the design goal of  residential noise insulation should be to achieve a noise level of 45  decibels in all habitable rooms; homes with interior noise levels already  below this level should not generally receive noise insulation. This  guidance does not explain the method by which a project sponsor needs  to assess interior noise levels. FAA district officials told us that the only  practical way to determine interior noise levels is with testing. FAA  officials indicated that airport sponsors generally conduct interior noise  testing on a sample of homes to determine eligibility based on the 45 dB  criterion and to assist in designing acoustical treatments, but  acknowledged that not all airports and consultants were consistently  applying these rules. We found that interior noise assessments to  determine project eligibility had been conducted at only three of the six  airports we visited with residential noise insulation programs. Two of the  three airports tested samples of homes, and officials at one of these  airports noted that, to date, no homes have been excluded based on  testing results because all had tested above DNL 45 dB. The third  airport’s program included interior noise assessment for all homes in the  DNL 65-69 dB contour to determine eligibility prior to including a home in  the insulation program. In that program’s current phase—focused on  homes in the DNL 65-69 dB contour in the airport’s noise exposure  map—less than half of the homes qualified for insulation following testing.  We also found that testing protocols differed at these three airports. For  example, some tests used artificial noise to simulate aircraft noise while  other test procedures relied on actual flyovers. The other three airports  we visited did not conduct interior noise assessments for eligibility, but did  do some testing for project design purposes. However, without  information on testing practices at all airports performing residential noise  insulation, we cannot determine the extent of the risk to federal  investments or how much, if any, AIP noise grant funding has gone to  projects that did not meet the eligibility criteria.
Residential noise insulation projects may not have been limited to  residences that have interior noise levels above DNL 45 dB because FAA  has not consistently and routinely implemented criteria on interior noise  level assessment. These criteria do not delineate requirements and  protocols in detail. FAA officials explained that implementation has been  inconsistent because airport officials, airport consultants, and FAA district  officials have different interpretations of existing program criteria. FAA  guidance did not, for example, specify testing protocols fully. Further, as  with updating noise maps, there are disincentives for airports to rigorously  implement existing criteria. For example, as a result of assessments  some residents may not receive expected benefits, such as acoustical  doors, windows, and ventilation systems. Airport officials often have to  deal with community discontent when they explain why some residents  are eligible for noise insulation and others are not.
At the time of our review, FAA, recognizing concerns about the age of  noise exposure maps and the inconsistent implementation of interior  testing criteria, issued program guidance in August 2012 to clarify existing  requirements regarding noise mitigation. According to FAA officials, the  guidance reinforces existing criteria on grant eligibility regarding the age  and accuracy of noise exposure maps and clarifies the DNL 45 dB interior  noise eligibility criteria. The guidance also addresses how interior noise  should be measured and will provide for a 3-year transition period that will  allow airports to continue with promised noise mitigation projects while  better aligning projects slated for 2014 and beyond with the eligibility  criteria. It is unclear whether FAA will fund projects during the transition  period that do not demonstrably meet program eligibility criteria. FAA  previously identified similar concerns about fund use and issued clarifying  guidance. Namely, the problems we found regarding potentially  inaccurate and old noise exposure maps were also identified in a 2002  internal FAA study.and 2001, grants were provided to airports based on potentially  inaccurate maps from the 1980s and early 1990s that pre-dated the  stage-2 aircraft phase-out. The study indicated that, because of shrinking  contours, some grants may have funded projects in moderately noise  impacted areas (DNL 55 to 64 dB) that should not have been funded. To  address this issue, in 2003, and again in 2005, FAA issued program  guidance requiring that all grant decisions be based on noise exposure  maps that are less than 5 years old or otherwise certified as a reasonable  representation of conditions at the airport. Therefore, it will be important  that FAA enforce and its district offices adhere to the new guidance to  ensure that noise grants are both eligible and targeted to the highest  needs.
section_title: FAA’s Strategic Goal for Noise Reduction Is Not Linked to Noise Grant Program
paragraphs: FAA has established an overall agency goal for addressing airport  noise—which covers all noise-related agency efforts, not just the AIP  noise grant program—to reduce the population living in significantly noise   This goal  impacted areas to below 300,000 people nationwide by 2018.is articulated in the Department of Transportation’s fiscal year 2013  performance plan, FAA’s long-range strategic plan—Destination 2025— and other FAA performance documentation. The intended outcome of  reaching this goal is to ameliorate community noise concerns such that  they are not a constraint on airport growth. To achieve this goal and  outcome, the department and FAA have indicated that people still  exposed to significant airport noise levels shall be addressed by AIP  noise grants, FAA’s largest program to address airport noise, primarily  though airport-specific Noise Compatibility Programs.
However, the overall strategic goal is not linked to the results of the AIP  noise grants. We have previously reported that linking program  performance to overall goals can provide a clear, direct understanding of  how program results will lead to the achievement of goals. We have also  reported that to determine whether goals are met, an agency should  establish performance measures that gauge progress toward desired  outcomes and can be used as a basis for decision making. However,  with the exception of AIP-funded land acquisition and relocation projects,  the types of projects funded by AIP noise grants are not intended to lower  the number of people living in significantly noise-impacted areas, but  rather mitigate the negative impacts of airport noise exposure.words, noise grant results will not help the agency achieve its goal, as  articulated. Further, by articulating its goal strictly in terms of the  residential population exposed to significant airport noise, FAA has  established a strategic goal that does not account for the results of its  largest noise program. Specifically, neither the goal nor FAA’s use of the  MAGENTA tool to measure progress toward that goal by estimating the  population exposed to different levels of airport noise reflects AIP noise  grant results:   In other
The residential population goal and associated annual estimates of  population exposure do not take into account the number of residents  benefiting from AIP-funded acoustically treated homes. While these  residents continue to live in a noise impacted area, they do so in a  quieter home that has benefited from AIP-funded mitigation.
The goal and measure also do not account for student or other  populations using public buildings that may be affected by airport  noise and could benefit from the AIP grant program in the future.
As a result of establishing a strategic goal and a corresponding measure  of progress that do not account for AIP noise grants results, there is  insufficient performance information about the nature and extent of  remaining airport noise exposure and the contribution of noise grants in  mitigating the impact of that exposure. Specifically, FAA does not know  how many residences, schools, or other public buildings are in  significantly noise exposed areas or which of those have yet to benefit  from noise insulation projects. Without this information, Congress and  FAA program managers cannot make fully informed decisions about what  the noise grant program can reasonably be expected to address in the  future and the extent to which noise exposure remains a constraint on  growth. FAA officials acknowledged that the current approach could  cause confusion and that there may be some benefit to better  distinguishing between the agency’s overall noise goal and the purpose of  noise grants.
section_title: Airports Continue to Plan Noise Mitigation Projects, but of a Changing Nature
paragraphs: The 2011 National Plan of Integrated Airport Systems (NPIAS) report,  which includes airport projects from fiscal years 2011 through 2015,  shows continued plans for noise mitigation projects, but a drop in the  number of projects and the number of airports planning them.  Additionally, since the 2001 NPIAS report, the nature of included projects  has changed, reflecting airports’ progress in implementing their noise  compatibility programs, and a corresponding drop in the residential  population living in areas around airports deemed significantly affected by  noise. The change in the nature and extent of noise mitigation projects in  the NPIAS combined with other indicators—such as the age of NCPs,  shrinking noise contours, and other factors—points to the possibility of a  future decline in the demand for noise project funding. Concurrently, the  scope of projects eligible for the set-aside has expanded to include water  and emissions projects, whose cost may grow in the future.
subsections: section_title: Planned Noise Mitigation Project Demand
paragraphs: The NPIAS, which inventories airport projects planned over the next 5  years, is one indicator of future noise grant demand. The most recent  NPIAS, issued in 2011, illustrates that, as compared to previous years,  fewer airports are planning fewer noise mitigation projects, albeit at a  higher total cost. The 2011 NPIAS report to Congress includes planned  AIP-eligible projects. The number of airports with planned AIP noise  mitigation projects has declined 16 percent since the 2001 report, which  covered fiscal years 2001 through 2005, and the number of planned noise  projects included in the 2011 NPIAS is nearly half what it was in 2001  NPIAS. Despite the decreased number of planned projects, the  anticipated costs for those projects rose to $2.1 billion, or roughly $425  million per year.planned projects at airports as reported through the NPIAS since 2001.
Table 1 shows the number and estimated costs of   However, some airports are nearing the end of their  Furthermore, airports have developed fewer new or updated NCPs in  recent years, suggesting that future demand for noise grants may be  waning as existing programs mature. As noted previously, since AIP  noise grants were established in the early 1980s, FAA has approved  NCPs for 234 airports and inclusion in an NCP is a prerequisite for AIP  funding, with limited exceptions. About 85 percent (198 of 234) of the  airports’ NCPs were approved more than a decade ago, and since 2007,  only 14 new ones have been approved (see fig. 8).
Some communities around airports that are exposed to significant airport  noise are not likely to receive residential noise insulation. Airports are free  to choose not to perform residential noise insulation projects because  developing an NCP—a necessary step for the airport to take to receive  AIP funds for such projects—is voluntary. According to FAA and as would  be expected, 30 years into a voluntary program, airports that are likely to  pursue AIP-funded residential noise insulation programs have likely  already at least begun to do so. Some of the busiest airports in highly  populated areas have chosen not to complete an NCP. For example,  officials from the Port Authority of New York and New Jersey indicated  that they have not conducted Part 150 studies for any of the five airports  under their jurisdiction because a residential noise insulation program  would not alleviate noise exposure when people are outside their  homes—they noted that noise complaints peak in the summer—and AIP’s  grant-matching requirements would be financially prohibitive. To the  extent that airports without NCPs continue not to participate in the Part  150 program, the people living in areas significantly impacted by airport  noise may never receive the benefits of noise mitigation.is about a third of the remaining population that FAA’s MAGENTA model  estimated is exposed to significant airport noise. Specifically, in 2010, the  model estimated 113,000 people (out of 323,000) lived near airports that  had not developed an NCP, though this population is not monitored as  part of FAA’s strategic goal and measurement approach discussed  above.
Given the shrinkage of noise contours previously discussed, it is possible  that if airports updated older NCPs and noise exposure maps, some  noise projects in the current NPIAS—which reflects projects in NCPs— would no longer meet grant eligibility criteria. These smaller noise  contours would also reflect that the residential population within areas  significantly impacted by noise has fallen dramatically. While there is no  way to determine how many planned projects—and the costs of those  projects—would no longer meet the grant eligibility criteria, the 2011  NPIAS includes planned projects in areas designated as DNL 65-69 dB at  61 airports. Eighteen of these 61 airports have over $770 million in  projects even though their noise exposure maps are more than 10 years  old; as noted previously, these maps are likely to overstate current noise  exposure and funding to these projects could put federal investments at  risk. if sustained, suggest that projects approved under updated NCPs could  tend to be smaller in scale and scope.
section_title: Technology and NextGen
paragraphs: Some of these 18 airports may have other noise exposure maps that are more recent  because of, for example, an environmental assessment. FAA data would not include these  maps. anticipates that there will be noise exposure reduction benefits resulting  from the implementation of some operational changes, such as flight  procedures. For example, new arrival procedures will involve less engine  thrust, and thus result in quieter approaches. But even with these  benefits, changes in flight paths will affect populations that had previously  been subjected to less aircraft noise or less concentrated flight paths.  This impact, however, would generally remain outside the DNL 65 dB  contour and, unless the minimum eligible DNL were lowered, would not  affect grant demand. FAA has not yet determined the extent of the impact  of such operational changes on airport noise, and whether or how they  might change noise contours or lower noise exposure around an airport.  In contrast, the increases in air traffic predicted in the next decade,  particularly at airports near large, densely populated urban areas, could  result in recently contracted noise contours growing larger, which could  offset, to some unknown degree, advancements in technology and  operations. However, if noise contours reverse course and begin to  expand, some of that expansion could be into areas that already have  been remediated through previous noise mitigation efforts. In such cases,  newly eligible noise mitigation projects would not result. Conversely, new  incompatible land uses created by subsequent airport development or  operational changes may be eligible for funding consideration.
section_title: Noise Mitigation Projects Will Compete with Other Projects for Noise Grants
paragraphs: In the future, more types of environmental projects will be competing for  the same amount of AIP noise grant funds. The amount of funding  available for noise grants is established by Congress. Recently, Congress  has expanded the eligibility for noise set-aside funding to projects not  directly related to noise, a change that has effectively decreased the  funding available for noise programs in recent years. In addition, the  Voluntary Airport Low Emission (VALE) program, which was designed to  reduce ground sources of emissions at commercial service airports  located in areas failing to meet or maintain EPA ambient air quality  standards, became eligible for noise grant funding in fiscal year 2005.  Under the VALE program, FAA made 51 grants during fiscal years 2005  to 2011 totaling $108.5 million at 30 airports. The 2011 NPIAS identifies  plans for $87.9 million in VALE projects at 11 airports through fiscal year  2015 (about 4 percent of the estimated cost of all AIP eligible noise  mitigation projects listed in the report). FAA airport district office officials,  as well as airport officials we interviewed, indicated that VALE projects  will continue to be pursued in the future. In addition to VALE, the 2012  FAA reauthorization expanded eligibility for certain water projects at  airports undertaken as a result of an environmental record of decision for  an airport development project, such as a runway extension. FAA has  not estimated future demand for VALE. And because the water project  eligibility is new, no such projects appeared in the 2011 NPIAS report and  FAA has yet to determine how these projects would be ranked against  VALE and noise mitigation projects. Therefore, it is not clear how  expanded eligibility for these other kinds of projects for AIP noise set- aside grant funds may affect FAA’s ability to meet future noise grant  demand.
section_title: Conclusions
paragraphs: Today, the number of people in the United States who are exposed to  significant airport noise is considerably reduced from when FAA began  providing AIP noise grants in the early 1980s. Overall, the program has  benefited thousands of people over the years by mitigating airport noise— one of the top environmental concern of airports. However, in the  decades since the AIP noise grant program began, airports have  completed numerous noise mitigation projects and technology has  produced quieter aircraft and better operating procedures. Our review  shows that, now and going forward, the need for noise grants may be  lower than it was in the past. It is up to FAA to ensure that  future noise grants are directed to the remaining projects that meet  the grant eligibility criteria,  the agency’s goal for addressing airport noise aligns with the current  airport noise problem, and  the measures used to assess progress accurately reflect FAA’s  programmatic results.
As implemented, there is a risk that some federal investments in noise  mitigation went to projects that may not have met existing eligibility  criteria, and if not effectively addressed, this risk will continue in the  future. FAA has not uniformly enforced the accuracy of noise exposure  maps and has inconsistently applied program criteria for interior noise  assessments. This diminishes Congress’s and the public’s assurance that  federal funding has been or will be spent appropriately and, to the extent  that some misapplication of AIP grants to projects has occurred, creates  the risk that more meritorious projects at other airports may not have  been funded. It is encouraging that FAA issued guidance to more clearly  articulate the program’s eligibility criteria and has called upon airports to  review their noise programs to better ensure the eligibility of planned  projects. If properly implemented and followed, this guidance should  reduce the risk of federal investment in ineligible projects. However, since  some of these problems have persisted despite previous FAA guidance, it  is too soon to tell if FAA’s current actions will be successful.
Currently, FAA’s overall goal for its noise efforts is to reduce the  population exposed to airport noise above DNL 65 dB to less than  300,000 people by 2018 and FAA measures progress by estimating the  residential population exposed to this noise level. However, there are  shortcomings to this approach. First, FAA’s overall goal is disconnected  from FAA’s primary tool to address noise—the AIP noise grants— because it does not reflect the results of these grants. Beneficiaries of  noise insulation projects continue to reside or attend school in DNL 65 dB  or louder areas even though the noise exposure has been mitigated for  them. Second, approximately one-third of the estimated remaining  population exposed to significant airport noise resides near airports that  have yet to and may never establish an NCP. After 30 years, it appears  unlikely that this population will ever be reached by the current program.  FAA’s strategic goal and measures do not account for this population. To  more effectively manage the program and target federal funds, goals and  metrics should align with the nature and extent of the remaining airport  noise problem. At present, however, the nature and extent of the  remaining airport noise problem are ill-defined. Key steps to effectively  address airport noise include understanding the nature and extent of the current problem, determining appropriate goals to address the problem, establishing metrics to measure progress, and using this information for decision making.
Effective program management should increase the effectiveness of the  current grant program and provide a more complete picture of noise grant  results. Though a number of airports continue to have planned noise  mitigation projects, after 30 years of funding noise grants, it is reasonable  to question whether the program may remain relevant for only a limited  period in the future or need to be reformed to better target emerging  needs. Increased knowledge about the problem and the use of noise  grants as a solution should help Congress and FAA chart the most  appropriate course for the future of the AIP noise program.
section_title: Recommendation for Executive Action
paragraphs: To better ensure that federal investments effectively address the  remaining airport noise problem and to more fully demonstrate the results  of AIP noise grants, the Secretary of Transportation should direct FAA to  take the following two actions:
Establish a strategic noise reduction goal that aligns with the nature  and extent of airport noise and targets the agency’s noise grant  program.
Establish performance measures to assess progress toward this goal  that better demonstrate the results of the program and provide  Congress and FAA’s program managers with information to gauge  progress and make programmatic decisions.
section_title: Agency Comments and Our Evaluation
paragraphs: We provided a draft of this report to the Department of Transportation  (DOT) for its review and comment. DOT and FAA officials provided  technical comments that we incorporated as appropriate. In addition, in  emailed comments to us, DOT offered several observations on our report.  First, DOT highlighted that the noise grant program is not the only means  by which airport noise has been reduced, noting that other FAA initiatives  and industry actions, especially those that led to improvements in aircraft  engine technology are primarily responsible for airport noise reductions.  We concur with this position but, as indicated in the report, the noise  grant program is the largest FAA expenditure to address noise. Second,  DOT officials stated their belief that noise grants only go to projects that  meet eligibility criteria unless otherwise justified. However, as noted in our  report, in light of the overall decline in airport noise, the age and potential  inaccuracy of some noise exposure maps, and FAA’s inconsistent  implementation of eligibility standards, we believe there is an increased  risk for noise grants and have noted the limited circumstances under  which grants can be made to projects that don’t meet these criteria. FAA’s  recent issuance of guidance clarifying eligibility criteria is commendable  and needed because, if properly implemented, it will address this risk.  Finally, DOT noted that FAA sets annual beneficiary targets for noise  grants, tracks progress toward these targets, and reports these results to  Congress. We acknowledged these actions in our report, but these  targets, results, and reporting are not linked to FAA’s strategic noise goal  and measurement approach nor are they included in FAA’s reporting on  progress toward that strategic goal. Without a linkage between the results  of FAA’s most costly program to address noise and FAA’s strategic goal  for addressing noise, Congress, FAA, and the taxpayers do not have  sufficient information on the value of these continued investments.
FAA reviewed our recommendations and agreed to consider them for  action.
We are sending copies of this report to the Secretary of the Department  of Transportation, the Administrator of the Federal Aviation  Administration, and appropriate congressional committees. This report is  also available at no charge on the GAO website at http://www.gao.gov.
If you or your staff have any questions about this report, please contact  me at (202) 512-2834 or dillinghamg@gao.gov. Contact points for our  Offices of Congressional Relations and Public Affairs may be found on  the last page of this report. GAO staff who made major contributions to  this report are listed in appendix II.
section_title: Appendix I: Objectives, Scope, and Methodology
paragraphs: This report addresses the following objectives: (1) how airports’ noise  exposure has changed since federal noise grants were first funded, (2)  how Airport Improvement Program (AIP) grants have been used by  airports to mitigate noise and what have these grants achieved, and (3)  the likely future demand for AIP noise set-aside grants.
To describe how airport noise exposure has changed over time, we  reviewed available literature and met with industry organizations. For the  purposes of this report, we used the currently accepted definition of  significant airport noise (e.g., DNL 65+ dB). We interviewed officials from  the Federal Aviation Administration’s (FAA) Office of Airports and the  Office of Policy, International Affairs and Environment at FAA  Headquarters, and at 4 Airport District Offices in 3 of 7 FAA regions. We  also performed a Geographic Information Systems (GIS) analysis of noise  contours at selected airports to illustrate the changes to areas exposed to  airport noise over time. To assess how the population exposed to noise  has changed over time, we obtained information from FAA’s MAGENTA  noise model. We did not independently assess the MAGENTA model  itself. FAA uses this model to estimate the population exposed to  significant airport noise. The MAGENTA estimates for noise exposure are  broadly used and generally considered accurate for the purposes  intended.
To assess how AIP grants have been used for noise project planning and  implementation, we obtained and analyzed data in FAA’s System of  Airport Reporting (SOAR). This database includes detailed information  about AIP grants, Passenger Facility Change (PFC) approvals, project  types, and other airport information. We assessed the reliability of SOAR  data by (1) performing electronic testing of required data elements, (2)  reviewing existing information about the data and the systems that  produced them, and (3) interviewing agency officials knowledgeable  about the data. We determined that the data were sufficiently reliable for  the purposes of this report. We met with sponsors of 7 airports in three  regions to discuss the development and implementation of their noise  compatibility programs. These airports were judgmentally selected to  provide information from airports of different sizes, different parts of the  country, and at different points in implementing their noise projects.  Information obtained from these airports is for illustrative purposes only,  and cannot be generalized for all airports. To understand how the results  of AIP noise grants have contributed to FAA’s progress towards achieving  its strategic noise goal, we assessed FAA’s use of its MAGENTA noise  model compared to GAO criteria.
To assess future demand for AIP noise grants, we reviewed planned  projects in the National Plan for Integrated Airport Systems (NPIAS),  FAA’s primary tool for identifying potential airport capital projects. The  NPIAS data is part of FAA’s SOAR reporting system. We also obtained  information about the dates of airports’ Noise Compatibility Programs  (NCPs) and noise exposure maps from the Office of Airports at FAA  Headquarters. For the purposes of this report, we used the currently  accepted definition of significant airport noise (e.g., DNL 65+ dB)—as  does the NPIAS—to identify potential future noise projects. The results of  our analysis of future demand for noise grants would change if the  definition of significant airport noise changes in the future. To understand  the implementation and future of airport noise programs, we reviewed  noise programs at the 7 airports indicated above and discussed them with  the 4 Airports District Offices which oversee those airports.
We conducted this performance audit from October 2011 through  September 2012 in accordance with generally accepted government  auditing standards. Those standards require that we plan and perform the  audit to obtain sufficient, appropriate evidence to provide a reasonable  basis for our findings and conclusions based on our audit objectives. We  believe that the evidence obtained provides a reasonable basis for our  findings and conclusions based on our audit objectives.
section_title: Appendix II: GAO Contact and Staff Acknowledgments
subsections: section_title: GAO Contact
section_title: Staff Acknowledgments
paragraphs: In addition to the individual named above Paul Aussendorf (Assistant  Director), Amy Abramowitz, Hiwotte Amare, Elizabeth Curda, Jeff Heit,  Dave Hooper, Christopher Jones, Delwen Jones, John Mingus, SaraAnn  Moessbauer, Josh Ormond, and John Stambaugh made significant  contributions to this report.