Frequently Asked Questions
The Piedmont Triad Airport Authority answers basic questions about the Part 150 Study Update below. We will add questions and answers to this list as the study progresses.
What is a Part 150 Study?
A Part 150 Study is a federally funded and supervised program that helps airports identify and find ways to reduce land uses around an airport that are not compatible with aircraft noise, according to compatibility standards established by the Federal Aviation Administration. The name “Part 150” comes from the fact that the studies are conducted under Title 14, Part 150, of the Code of Federal Regulations. Part 150 Studies include the development of Noise Exposure Maps (NEMs) to assess noise levels around an airport and associated land use and, at the election of the airport, can also include a Noise Compatibility Program (NCP), with measures to reduce non-compatible land uses.
What is the purpose of the current Part 150 Update?
The current study will update the Authority’s original Part 150 Study. The FAA accepted the Noise Exposure Maps from the original study, and with some minor revisions the FAA approved the Authority’s recommended Noise Compatibility Program measures in 2008. The current study will develop updated Noise Exposure Maps for the Airport for both current conditions and for conditions anticipated in a five-year forecast, and the study will review the measures in the Authority’s current Noise Compatibility Program for the Authority to determine what adjustments, if any, are needed to those measures.
Who conducts the update?
The Authority sponsors the update and is ultimately responsible for its findings. The Authority has hired a noise consultant, HMMH of Burlington, Massachusetts, to conduct the study with the help of two advisory committees, a Citizens Advisory Committee and a Technical Advisory Committee.
- Airport area residents appointed by local governments sit on the Citizens Advisory Committee.
The Technical Advisory Committee consists of (1) representatives of airport users, such as airlines, cargo carriers, HondaJet, HAECO, FedEx, Cessna and others with expertise in airport operations, (2) planners from jurisdictions around the airport, who advise the Committee about land use and (3) the Chair and Vice-Chair of the Citizens Advisory Committee.
Is the process public?
Yes. The update includes two informational public workshops. The first workshop, which has been held already, introduced the Study and the second workshop will present the results of the Study. The purpose of the workshops is to provide an opportunity for the public to review project materials, discuss the study with the Authority and to offer written comments. The Authority posts public notices of the Advisory Committee meetings, which are being held quarterly, and the public may attend the committee meetings, although participation in committee discussions is limited to the committee members. The public may also use the project website to review project documents and meeting materials here or comment or ask questions here. A newsletter about the study has been mailed to airport area residents. In addition, if the Authority’s Noise Compatibility Program is updated or amended, there will be a court reporter at the final public workshop to record oral comments from attendees.
How long will the study take?
The Part 150 Update Study, which began in the Spring of 2019, should take just over a year to complete.
What is the end product of the Part 150 Update?
The Part 150 Update will develop new Noise Exposure Maps, also known as noise contour maps, showing projected noise contours for the Airport for the years 2020 and 2025. The study will also review the Authority’s Noise Compatibility Program measures and recommend any changes that are deemed to be appropriate.
What is a Noise Exposure Map (NEM)?
A Noise Exposure Map is a scaled, geographic depiction of an airport, its noise contours, and the surrounding area developed in accordance with the methods described in Part 150. An NEM includes documentation required by Part 150 to show five-year forecast operations at the airport and to show the ways the forecast operations will affect the map. The noise contours show the areas within which aircraft noise is expected to equal or exceed DNL levels of 65, 70 and 75 dB. The contours are superimposed on a land use map of the area surrounding the airport to display the DNL noise exposure and the resulting land use compatibility.
What is the Noise Compatibility Program (NCP)?
A Noise Compatibility Program consists of measures to reduce areas that are not compatible with the level of aircraft noise that they are experiencing and to prevent the introduction of any new non-compatible land uses. Noise Compatibility Program measures fall into three categories: Noise Abatement Measures, including modified flight procedures, Land Use Measures, including residential sound insulation, and Program Implementation Measures. Compliance with NCP flight procedures is generally voluntary on the part of FAA Air Traffic Control and aircraft pilots.
Click here to view the Airport’s existing NCP.
Who has final approval of the Noise Exposure Maps and the Noise Compatibility Program?
Ultimately the FAA decides whether the new Noise Exposure Maps are compliant with Part 150. If a Noise Compatibility Program update or amendment is submitted, the FAA will approve or disapprove each of the recommended measures. The Authority has the ultimate responsibility for recommending the measures to be included in its Noise Compatibility Program rather than the project consultant or advisory committees.
How will the noise contours be developed for the Part 150 Study?
The noise contours on the Noise Exposure Maps will be generated by a computer modeling program (Airport Environmental Design Tool or “AEDT”), which is the modeling program prescribed by the FAA for noise studies. The input data for the AEDT includes a forecast of aircraft operations, on an annual average day, for each of the study years (broken down between day and night activity), runway utilization rates for aircraft types, flight track geometry for different aircraft types and other factors.
What do the decibel levels on the NEM noise contours represent?
The decibel levels represent the “Day-Night Average Sound Level”(“DNL” for short), which is a 24-hour average sound level, in decibels, for an annual average day of aircraft operations with a 10-decibel penalty attributed to nighttime operations (between 10 p.m. and 7 a.m.) The noise when aircraft are overhead is averaged with the times during the day when there is less or no aircraft noise, so the DNL level for a particular location is considerably lower than the highest decibel levels that might be heard at that location, or measured on a noise meter, during aircraft overflights.
Why is DNL used to develop noise contours rather than the sound level I hear when planes are overhead?
The FAA requires the Noise Exposure Map noise contours to be based on DNL, and for DNL to be used to assess land use compatibility. The advantage of DNL is that it reflects cumulative noise exposure and not just the noise level at a specific moment in time.
Does DNL take into account the time of day when noise occurs?
Yes. Each nighttime flight (from 10 p.m. to 7 a.m.) is assessed a penalty of 10 decibels. This is mathematically equivalent to counting a single nighttime flight the same as 10 identical day-time flights.
Does DNL take into account weather and topography?
Yes. A 30-year weather history is used to develop the new contours, so the contours reflect the effect of varying weather conditions on aircraft operations and on sound transmission. Topographic data is also used to model the noise experienced at different elevations around the Airport.
Will noise monitors be used to measure the noise at specific locations?
Measurements will be taken at six locations around the airport. Monitors will record noise measurements for approximately five days at each location. The monitoring results will be compared with the AEDT modeling calculations, will be shared with the Advisory Committees and will be posted on the project website.
Will the measurements from the noise monitors be used in developing the new Noise Exposure Maps for the Airport?
No. The FAA requires DNL contours to be developed through its computer modeling program rather than actual noise measurements. The input into the modeling program is far more comprehensive than could possibly be obtained from field measurements, and modeling is the only practical way of determining the noise that will be experienced at all of the geographic points that are represented in the noise contours. Noise modeling is also necessary to forecast the noise that is expected in the future, as required by Part 150. The FAA noise modeling program has been shown to accurately portray the results from measurements in the field.
Can homeowners arrange for their houses to be included in the noise measurements?
While the Authority understands homeowners wanting monitoring at their own houses, the selected sites will be at the approximate locations of the sites that were used in the original Part 150 study, making it possible to compare current results with the results from the previous monitoring.
Will the effect of runway closures be considered in the Part 150 update?
The closures of the Airport’s main runway (Runway 5R/23L) will not be reflected in the Part 150 update because the closures are temporary. The Part 150 Noise Exposure Maps and Noise Compatibility Program are based on normal operations, which are expected to resume when the rehabilitation work on Runway 5R/23L is complete.
Will the noise contours generated by the new study anticipate future conditions?
Yes. Two Noise Exposure Maps will be developed. The first will be based on air traffic projections for next year (2020). The second will be based on a forecast of air traffic for 2025.
Will ground noise be studied or only the noise of aircraft in the air?
The noise contours will take into account the engine noise as planes accelerate for take-off and reverse thrust as planes land. The contours will also take into account ground engine runups during maintenance and testing procedures.
Will consideration be given to the airport development that is now occurring in the vicinity of Runway 5L/23R?
It is not possible at this time to forecast the aircraft operations that might result from the development of new aeronautical sites around Runway 5L/23R, including the site that has been cleared north of I-73. While the Authority does not expect, at this time, that the planned use of these sites would involve a major increase in aircraft flights, if any new flights would cause a substantial new non-compatible land use in the five-year forecast NEM, as defined by FAA criteria, the Authority would develop new NEMs to reflect the increase.
Why is the Authority still showing the noise contours from the original Part 150 Study?
These contours were on display at the Part 150 workshop in June and are displayed on the Part 150 website because these are the current FAA-accepted Noise Exposure Maps for the Airport. The Part 150 update will revise the contours based on 2020 and five-year forecast aircraft operations.
Will the Part 150 Study be limited to identifying the noise that currently exists or will an effort be made to reduce noise exposure?
The Authority’s previous Part 150 study developed an NCP to reduce the effects of aircraft noise over residential areas. The FAA Record of Approval for the existing Noise Compatibility Program, with a description of the Noise Compatibility Program measures, can be found here. The current Part 150 update will consider whether changes should be made to the NCP.
Will my house be eligible for sound insulation as Part of the Noise Compatibility Program?
Under FAA noise compatibility criteria, houses are eligible for sound insulation only if they are located within the 65 DNL contour. The Authority has been conducting a sound insulation program within the existing 65 DNL noise contours for homes that were built prior to December 31, 2001 or that had a building permit or subdivision approval before that date. Under updated guidance that has been issued by the FAA since the eligible homes were identified for the Authority’s current program, houses must have an interior DNL level of 45 dB or greater in addition to having an exterior DNL of 65 dB or greater to be added to the program. Until the new Noise Exposure Maps are developed, it is not known whether additional houses will be included.
Does the Authority provide any assistance to homeowners who decide to sell their houses?
The Noise Compatibility Program for the original Part 150 Study included a measure for Purchase Assurance and Sales Assistance for homeowners who sell their homes. However, as in the case of sound insulation, these measures were limited to houses within the 65 DNL contour. Because the Authority has been sound insulating the homes within the existing 65 DNL contour, there has been no occasion to date for providing Purchase Assurance or Sales Assistance.
Where can I find copies of the display boards that were presented at the public workshop?
The display boards are posted in the Public Outreach page of this website, here.
Where can I find more information about aircraft noise?
See Frequently Asked Questions about Noise” here.
What if I have more questions about the Part 150 Update?
Questions or comments about the Part 150 Update can be submitted through this website or to firstname.lastname@example.org. While the Authority cannot answer each person’s questions individually, the Authority will review all questions and comments that are submitted through this website and decide whether new information should be added to these FAQs.
This page describes the overall Part 150 study process.
You will find background documentation, including maps and the 2008 report linked on this page.
This section presents an overview of the public outreach program, upcoming meetings, and summaries of completed meetings.
Please look here to find answers to frequently asked questions about the Part 150 Update Study.