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Aircraft Noise Measurements

Q. How is aircraft noise measured?
A. Aircraft noise is measured in A-weighted decibels (dBA) which approximates the way humans hear sound. The Federal Aviation Administration (FAA) and Environmental Protection Agency (EPA) both recognize and use the same metric for aircraft noise measurement. The industry standard for determining long-term aircraft noise exposure around airports is done using a methodology called Day/Night Average Noise Level (DNL), also known as LDN. The FAA has developed a computer model called the Integrated Noise Model (INM) which integrates the DNL metric to depict the noise exposure levels from aircraft around an airport onto a base map into noise contours of equal DNL, usually, into contour lines of 55, 60, 65, 70, and 75 DNL.

Example: One aircraft event occurs and then another aircraft event occurs 10 minutes later with both events registering a maximum noise level of 75 decibels each. Using the DNL metric, each aircraft noise event is added up and averaged together along with the quiet time or background ambient noise in between the events to arrive at a total DNL. Thus, the total DNL measured will be less than 75 decibels during that time period.

Each aircraft noise event is logarithmically averaged over a 24 hour period with a 10 decibel noise penalty added to all aircraft operations that occur between the hours of 10 p.m. and 7 a.m. This penalty is applied during the time most people are trying to rest.

Example: The 10 decibel noise penalty when applied to ten aircraft takeoffs occurring between the hours of 10 p.m. and 7 a.m. is acoustically equivalent to 30 aircraft takeoffs during daytime hours.

To learn more about aircraft noise measurement, see the Federal Interagency Committee on Aviation Noise (FICAN) document, How do we Describe Aircraft Noise?

Q. What is the limit on aircraft noise? How loud is loud?
A. There is no specific limit on aircraft noise. See the chart which gives sound level comparisons of aircraft compared to other sources of noise.

Aircraft noise levels are federally regulated by the Federal Aviation Administration (FAA) under Federal Aviation Regulation (FAR) Part 36. This regulation proscribes the measurement criteria and records the noise level measurements taken on three phases of flight at three different measuring points for landing, takeoff and sideline noise on all manufactured aircraft.

Part 36 also designates Stage ratings for helicopter and jet aircraft. In 1977, three "Stage" categories of jet ratings were developed, Stage 1, 2, 3 and Stage 4. A Stage 1 rating is considered the noisiest, Stage 2 rating less noisy, and a Stage 3 rated jet aircraft being the quieter and the Stage 4 standard adopted in 2006 being the quietest. Stage 1 category jets are pure jet aircraft, such as, military jet aircraft and/or early commercial and corporate jet aircraft built in the 1950's and 1960's. Stage 2 rated jets are also older manufactured jets primarily built in the 1970's and into the early 1980's.

Stage 3 rated jets are those built with the latest technology using quieter turbo-fan jet engines built in the late 1980's and since that time forward. Any jet aircraft certificated and manufactured after January 1, 2006 will have to meet Stage 4 noise standards. Today's modern jet aircraft have made major reductions in the noise they create on both takeoff and landing operations which has helped to reduce their overall noise impacts to communities surrounding airports.

Under a 1990 Federal law, the Aircraft Noise and Capacity Act of 1990 (ANCA), the U.S. Congress mandated that all Stage 2 rated commercial turbojet aircraft of 75,000 lbs. or greater had to be phased out by Dec. 31, 1999. Thus, all U.S. airlines that operated Stage 2 rated jet aircraft in their fleets, had to replace, sell, or equip these aircraft with engine hush-kits to meet the more stringent and quieter Stage 3 jet rating requirements.

In Feb. 2012, President Obama signed into law the FAA Modernization and Reform Act of 2012. Under this law, the U.S. Congress has mandated the phase out and elimination of Stage 2 rated jet aircraft under 75,000 lbs. by Dec. 31, 2015. The law primarily affects private/corporate operators of older business jet aircraft who will now have to meet the current Stage 3 noise limits by either modifying or selling these aircraft.

Q. Can a loud aircraft be fined?
A. No, our office cannot levy a fine or otherwise penalize an aircraft operator for the amount of noise an aircraft makes. We do not have the legal authority to do so regardless of how noisy it was. However, we will work with operators to assist them in reducing their noise levels through the use of our Airport Noise and Operations Monitoring System (ANOMS) which consists of 22 fixed noise monitors around the airport. The airport manages a High Range Noise Event (HRNE) Program whereby our office measures and monitors loud aircraft noise events in the surrounding communities and contacts all aircraft operators who cause noise events of 90.0 decibels or higher at our noise monitors.

Q. Can you tell me how loud that aircraft was?
A. Maybe, provided that we have a noise monitor located near your home and the noise was picked up and data recorded at that monitor. We could then provide you with that information.

Q. Do I have a noise monitor in my area?
A. The airport has 22 permanent noise monitors located within a 12 mile radius of the airport. We have 18 noise monitors located in 8 towns in Westchester County and 4 noise monitors located in Greenwich, Connecticut. There may be one located near you depending upon where you live. See our noise monitor street address and location map. A fixed permanent noise monitor installation is expensive and should be located on public right-of-way for easy access for maintenance and near utility connections. A fixed noise monitor station has to be properly sited in order to obtain good quality noise data from the unit. Our office does have two portable noise monitors which can be taken out into the field to perform noise studies in areas where no permanent noise monitors are available or close enough to the study location to measure noise.

The County of Westchester undertook a Noise Monitoring Site Analysis Study in 1999 to evaluate the existing 14 noise monitor locations for possible relocation and to also investigate the potential addition of new noise monitor sites for better geographic coverage of aircraft noise around the airport. This was a public process that requested the public's input and included two public workshops, notification of all surrounding towns, public officials and callers at that time. The study recommended the addition of six new sites and the relocation of six existing sites. Only the preexisting site of RMT #13 in the Belle Haven section of Greenwich was not relocated at the request of the neighborhood. The relocated sites are now indicated with the letter R and the new Remote Monitor Terminal (RMT) sites were numbered 15 through 20. In April 2002 all the new and relocated monitor sites went on-line and their noise levels published for the first time.

In late 2009, the County of Westchester did add a new noise monitor terminal in the towns of Briarcliff Manor and Pound Ridge, New York. This was done in order to measure background community and aircraft noise levels prior to anticipated future changes in flight paths by the Federal Aviation Administration (FAA) as part of the implementation of their NY/NJ/PHL Airspace Redesign Project. The FAA's own noise model predicted increases in aircraft noise levels over both towns due to the proposed shifting in the LaGuardia and Westchester arrival flight paths further east and a new proposed northwesterly departure track at Westchester. This was the impetus that led to the installation prior to the airspace changes over Westchester County taking effect.

Q. Can you tell me what noise contour I live in?
A. Yes, we should be able to determine what noise contour you reside in using the most recent contour map we have available. Please note that the FAA has determined that land area inside of the 65 DNL or higher DNL noise contour is considered incompatible for residential land use. The very first noise contours for the Westchester County Airport were done for the year 1988. The most recent noise contour study update was done in 2001 and published in August 2002. This 2002 report produced the actual 1999 noise contours around the airport and also forecasted the contours for 2005. Here is the most recent contour map available. In 2012, the airport began the process of developing a new airport master plan that will provide for the short and long term future plans and projects for airport development over the next 20 years. A part of this process will include a run of the Integrated Noise Model (INM) to generate a new and more current noise contour map around the airport as part of the Master Plan's Environmental Assessment (EA).

Q. Has the airport ever done a Part 150 study?
A. No, the County of Westchester has never elected to do a CFR 14 Federal Aviation Regulation (FAR) Part 150 Airport Noise Planning and Land Use Compatibility Study. This is a voluntary program sponsored by the FAA that will provide Federal funding for noise mitigation projects. If your Part 150 program is approved by the FAA, federal funding would be made available to pay for approved noise mitigation projects around the airport including noise abatement programs and procedures along with any land use control measures.

Aircraft Altitudes

Q. What can be done about low flying aircraft and helicopters?
A. Aircraft and helicopter altitudes are regulated by the Federal Aviation Administration (FAA) under Federal Aviation Regulation (FAR) Part 91. Regulation Part 91.119 mandates the minimum safe altitudes for aircraft and helicopters. Also, the local FAA Control Tower air traffic personnel or FAA Terminal Radar Approach Control Facility (NY TRACON) will also assign altitudes to aircraft while in flight. The rule below is to be found in Title 14 Code of Federal Regulations under Subpart-B Flight Rules Section 91.119. See below, Federal Aviation Regulation (FAR 91.119).

91.119 Minimum safe altitudes: General.
Except when necessary for takeoff or landing, no person may operate an aircraft below the following altitudes:

(a) Anywhere. An altitude allowing, if a power unit fails, an emergency landing without undue hazard to persons or property on the surface.

(b) Over congested areas. Over any congested area of a city, town, or settlement, or over any open air assembly of persons, an altitude of 1,000 feet above the highest obstacle within a horizontal radius of 2,000 feet of the aircraft.

(c) Over other than congested areas. An altitude of 500 feet above the surface, except over open water or sparsely populated areas. In those cases, the aircraft may not be operated closer than 500 feet to any person, vessel, vehicle, or structure.

(d) Helicopters, powered parachutes, and weight-shift-control aircraft. If the operation is conducted without hazard to persons or property on the surface.

(1) A helicopter may be operated at less than the minimums prescribed in paragraph (b) or (c) of this section, provided each person operating the helicopter complies with any routes or altitudes specifically prescribed for helicopters by the FAA; and

(2) A powered parachute or weight-shift-control aircraft may be operated at less than the minimums prescribed in paragraph (c) of this section.

Q. Was that aircraft flying at an illegal altitude?
A. Our office has the ability utilizing our Airport Noise and Operations Monitoring System (ANOMS) to research the altitude of an aircraft in flight provided we have the radar data available. We could then provide you with a map showing you the radar track and an altitude plot on this flight. The Federal Aviation Administration (FAA) is the only agency of government that can take any action against an aircraft operator for violating any altitude regulations or Air Traffic Control instructions. The FAA requests that anyone seeing an unauthorized low-flying aircraft to report it to your nearest Flight Standards District Office (FSDO) or FAA Air Traffic Control facility to investigate. You will need to provide the FAA with all the information and details you can about the incident for the possible identification of the aircraft. If you can get the aircraft registration number or "N" number, i.e. N1234X, that would be helpful or any photographs or video of the event that may aid the investigation. See FAA Low-Flying Aircraft pamphlet.

Airport Curfew

Q. I thought there was a curfew?
A. The airport has no mandatory curfew. A curfew implies a legal or statutory prohibition against operating during certain hours. The Westchester County Airport is a public-use facility open 24 hours a day. The airport does have a Voluntary Restraint From Flying (VRFF) Program which is in effect daily from midnight to 6:30 a.m. It is a completely voluntary program whereby all operators are encouraged not to operate and avoid flying during these hours.

Q. How can we get a curfew here at Westchester?
A. The Westchester County Board of Legislators imposed a mandatory curfew by law back in 1981. The County of Westchester was sued and lost the case to impose a curfew in Federal court. See VRFF Fact Sheet here. The Court permanently enjoined the County of Westchester from ever imposing a curfew. In 1990, the U.S. Congress passed the Airport Noise and Capacity Act of 1990 (ANCA) which made it very difficult for any airport operator to impose a curfew or use restrictions in the future. All U.S. airports which had curfews or use restrictions in place at the time this law was passed were "Grandfathered" in and kept. The U.S. Congress would have to modify and change this law to allow airport owners to impose new restrictions. The airport could also choose to conduct a Part 161 Study (Notice and Approval of Airport Noise and Access Restrictions) under ANCA in an attempt to impose a use restriction pursuant to the Federal Aviation Regulations (FAR) Part 161. This is a legal process setup by the FAA which would require public notification, public input, scientific study, economic cost/benefit analysis and federal documentation. Any proposed changes would have to meet the approval of the FAA before the airport could implement any restriction. Since the ANCA law was passed, only Naples Airport in Naples, Florida has been successful in imposing a ban on Stage 2 noise rated business jets from operating, but only after many years of costly litigation with the FAA over this restriction.

Q. What can you do about these violators of the VRFF Program?
A. All operators who fly between the hours from midnight to 6:30 a.m. are contacted via letter by the Environmental Department and reminded to abide by the VRFF Program whenever possible. There are no fines or penalties that the airport can impose upon any operator who does not comply. Many of our based aircraft operators and frequent transient users do make the effort not to fly during this time. However, circumstances out of their control will sometimes cause a late arrival or necessitate an early departure to meet their travel requirements. Many operators will call ahead of their trip to confirm the nighttime hours of VRFF Program in an attempt to comply with the program and be good neighbors. The program is more effective to a certain extent, with our based corporate tenants and general aviation community who are based and live here. The real difficulty is getting some of the transient charter for hire operators, corporate and fractional owners from flying during this time. Also, some airlines do schedule departures prior to 6:30 a.m. in order for
their passengers to be able make the flight connections at their hubs to other destinations.

Flight Paths

Q. Have the flight paths been changed?
A. No. There have been no changes made to the flight paths here at Westchester. However, the Federal Aviation Administration is currently implementing a project to redesign the airspace overhead our area to reduce congestion and delays at LaGuardia (LGA), John F. Kennedy International (JFK), Newark Liberty International (EWR), Teterboro (TEB) and Philadelphia International Airport (PHL) and improve air traffic control operational efficiencies. This project is called the NY/NJ/PHL Metropolitan Area Airspace Redesign Project which started back in 1998.

Q. Would your office know if the flight paths have been changed?
A. Yes, our office would know if any flight paths have been "officially" changed by the FAA at Westchester. The County of Westchester, airport management, and noise office do not have any authority to move or change flight paths. The FAA exercises the sole authority and control over the entire airspace in the U.S. All stakeholders along with the surrounding communities would be notified through a public process about any flight path changes allowing for a public comment period. Also, depending upon what the change is, the FAA may be legally required to conduct an Environmental Assessment (EA) and/or Environmental Impact Study (EIS) to determine what, if any, environmental impacts would result from the proposed change. Also, your local Congressional offices and staff would be involved and participating in this process.

Q. When were the flight paths established?
A. The flight paths for fixed winged aircraft were designed by the FAA, local citizens from NY and CT and airport management representatives sometime in the early 1970's. In 1977, the current noise abatement procedures were designed into the Standard Instrument Departure (SID) and Standard Terminal Arrival Routes (STARS) for the airport. The airport's four helicopter routes (November, Echo, Sierra and Whiskey routes) for inbound and outbound use were established in 1982. These routes were incorporated onto the NY Helicopter Route Chart in 1995.

The Airport

Q. Are there any plans to expand the airport?

A. No. There are no plans to expand the airport. There are no plans to lengthen or strengthen the runways to accommodate larger, heavier aircraft to increase capacity. Modest improvements will be made in the main terminal from time to time. In 1985, the Westchester County Board of Legislators adopted a "Statement of Airport Policy", Resolution 266-1985 aimed at keeping the Westchester County Airport primarily a general aviation airport with limited commercial airline service.

Q. What is the so called "Terminal Use Agreement (TUA)" or "Terminal Use Regulation (TUR)"all about?
A. The TUA was a legal agreement reached between the County of Westchester and airlines which provide service here at the airport. This came about as a result of legal action back in 1984, also known as the "Midway Stipulation." This case involved Midway Airlines et al and its desire to serve the Westchester market which was denied back at that time. In 1985, the County of Westchester and the existing airlines entered into a 10 year agreement which then became known as the "Stipulation." The Stipulation agreement was designed to regulate and limit air carrier growth here at the airport. The County and the airlines agreed to a passenger capacity limit of 240 passengers per half hour across 4 available ramp positions for a maximum of 4 flights per half hour. In 1994, a new agreement was reached, called the "Westchester County Airport Terminal Capacity and Extension Agreement." The term of this agreement commenced on January 1, 1995 and continued in force until December 31, 2004. In 2004, the County completed the process of making the TUA with the approval of the FAA and airlines into the TUR and permanent by codifying it into County law under Section 712.462 Westchester County Airport Terminal Use Procedures in 2005. This regulation is consistent with Federal law and applies to all commercial airlines utilizing the main terminal building and terminal ramp.


Q. How is the 240 passenger limit monitored?

A. The airport tracks the number of enplaning and deplaning passengers on a monthly basis. This passenger number is averaged over a one month period to determine whether an airline is exceeding its Passenger Allocation for any half hour period. This effectively restricts the maximum number of passengers to 480 per hour and limits the airlines to a maximum of 8 flights per hour. If an airline exceeds its allocation of passengers they must correct it within the next month. If an airline violates its allocation of passengers and does not correct, the airport would notify them and could take away that particular slot. All airlines serving the airport must participate in a lottery system which is conducted quarterly to determine their flight slots, expected number of enplaning or deplaning passengers and type of aircraft to be used.

Employment Relationship

Q. Who do you work for?
A. We work for a private company, AFCO/AvPorts which is based in Dulles, Virginia and contracted by the County of Westchester to act as the operating agent for the airport. This management contract commenced on 6/1/1996 and expires on 5/31/2022. The airport staff reports directly to the Commissioner of Department of Public Works & Transportation.

Caller Relationship

Q. What are you going to do for me?
A. Our staff will investigate your complaints and attempt to identify what aircraft/helicopter caused your complaint(s), evaluate and analyze the particular situation, and if necessary, follow up with action. Callers can request a call back or copies of their complaints with our findings.

Noise Abatement Office functions

Q. What do you do?
A. The noise abatement office is staffed to monitor and measure compliance with our noise abatement programs and procedures. It is here to help educate, answer and respond to all citizen and governmental concerns regarding airport noise and to also work with aircraft operators and Air Traffic Control to reduce the noise impacts caused by airport operations. We have a 24 hour noise complaint hotline for citizens to call in complaints or if they prefer, send electronically in via the airport's website. We operate a computerized noise monitoring installation called the Airport Noise and Operations Monitoring System (ANOMS) that consists of 22 permanent noise monitors around the airport to measure the noise and impact of airport operations and allow airport staff to compile noise data and operational statistics for analysis and reports.

Our main noise abatement programs are:

  • Voluntary Restraint From Flying (VRFF) Program – Midnight to 6:30 a.m. daily
  • High Range Noise Event (HRNE) Program – threshold set at 90.0 decibels
  • Prohibition of intersection takeoffs of heavy aircraft > 12,500 pounds
  • Engine maintenance run-up restriction from 9 p.m. to 9 a.m.
  • Noise Abatement arrival and departure paths for all runways and routes
  • Limitations on the use of reverse thrust
  • Prior permission required to operate aircraft greater than 120,000 pounds

Community Involvement

Q. Are there any community or environmental groups, I can contact?
A. Yes, there are.

  • The Natural Resources Defense Council located in New York City
  • Local chapter of Sierra Club
  • The Westchester County Airport Advisory Board (AAB)
  • Check with your local town hall

The AAB conducts public meetings once a month in the Main Terminal Building, in the 2nd Floor conference room at 7:00 p.m.