Nextgen PBN Noise Consultant Washingtondc
Ginger Mattox Notes from N.O.I.S.E. workshop in Austin Texas on November 19, 2014
Ambose Clay
NextGen PBN Noise Consultant – WashingtonDC
Advisory Board to PARTNER (Partners Air Transportation Noises Emission Reduction) ASCENT - Centers of Excellence (COEs)
ARAC - FAA Aviation Rulemaking Advisor Board
ACRP-02-48 - NASTRBAirport Cooperative Research Panel
-Helicopter Noise Technical Research Group
College Park, Georgia City Councilman
-Hartsfield-JacksonAtlantaInternationalAirport flightpath consultant
Moving an established flight path is like moving a Highway. When you build a Highway you do not move it wily-nily. Land use maps are utilized to determine the best routes of travel. Business and industry grow up around those land routes.
Flightpaths are Highways in the sky. They are created in a similar fashion. Land use maps are employed to determine what topography is below: commercial, industrial, residential, historic, recreational, wilderness, native lands or archeological sites. The National Environmental Protection Act (NEPA) has standards set for each and every landscape. If the standard is met that determines there will be no significant impact to the environment, a “categorical exclusion” is issued that allows a Federal Agency to proceed with their plan of action
It is the responsibility of elected officials and local airport authorities to monitor purported changes that may affect the community at large. Negotiations should take place between the FAA, airport authorities and elected officials on behalf of their constituency before a new “Order” is implemented.
Performance Based Navigation (PBN) “Orders” require that the FAA show improved safety, efficiency, fuel savings, improved CO2 emission and a reduction in aircraft noise. The deadline that Congress has set for implementing NextGen in the US is 2020.
The noise standard that is used by the FAA is an A-weighted decibel scale (dBA). This means that what they load into the noise simulator is mid-range frequencies only. Although most aircraft noise can be measured on the A scale not all air traffic noise pollution is mid-range.
In fact, helicopter blade slap is a good example of low-frequency noise which is measured on the C-weighted decibel scale. dBC also measures high-level frequency like that produced by high-pitched engine whine.
Environmental factors also play a big part in the noise level frequency that is heard on the ground called “Community Tolerance Level”. Example: the Doppler Effect is the change in the frequency of a wave as it moves past the observer relative from the source. The most annoying ground level noise heard from an aircraft is the “backwash” of sound. The lower a plane flies, the louder the “backwash” on the ground.
Low level frequencies are particularly harmful to older structures that are built with rigid materials like stone or brick-n-mortar then placed on foundations that were not designed to give under stress. Historical, architectural, archeological and cultural recourses fall into this category. Modern structures made of flexible framing materials and set on foundations that are forgiving to ground vibrations are less likely to be affected by low frequency waves.
Another FAA standard that comes into play when determining noise level is the Day/Night Average Sound Level (D/NL) Day-Night Average Sound Level is an A and time-weighted average sound level normalized to a 24 hour period. Any measurement between 10:00pm and 7:00am is charged with 10X the amount of noise. An increase in 10dB doubles the sound heard by the receiver.
Mr. Clay then referred us to: FAR Part 150 (see my research below)
Quoting from Government documents:
FAA cites Ldn = 65 dB as a guideline for defining compatible land use in the vicinity of an airport (FAR Part 150, “Noise Control and Compatibility Planning For Airports”), and as part of the definition of a threshold for defining a significant noise impact (FAR Order 1050-1E, “Environmental Impacts: Policies and Procedures,” as follows:
4.3 SIGNIFICANT IMPACT THRESHOLDS. A significant noise impact would occur if analysis shows that the proposed action will cause noise sensitive areas to experience an increase in noise of DNL 1.5 dB or more at or above DNL 65 dB noise exposure when compared to the no action alternative for the same timeframe.
When the Ldn = 65 dB threshold of significance is exceeded, FAA policy permits, but does not require, further analysis to lower noise levels as follows:
14.4c. In accordance with the 1992 FICON (Federal Interagency Committee on Noise) recommendations, examination of noise levels between DNL 65 and 60 dB should be done if determined to be appropriate after application of the FICON screening procedure (FICON p.3-5). If screening shows that noise sensitive areas at or above DNL 65 dB will have an increase of DNL 1.5 dB or more, further analysis should be conducted to identify noise-sensitive areas between DNL 60-65 dB having an increase of DNL 3 dB or more due to the proposed action. The potential for mitigating noise in those areas should be considered, including consideration of the same range of mitigation options available at DNL 65 dB and higher and eligibility for federal funding. Page 13 This is not to be interpreted as a commitment to fund or otherwise implement mitigation measures in any particular area. (FICON p. 3-7).
When the Ldn = 65 dB threshold of significance is exceeded the FAA policy permits, but
does not require further analysis using supplemental noise metrics as appropriate to the
situation:
14.5a. The Federal Interagency Committee on Noise (FICON) report, “Federal Agency Review of SelectedAirport Noise Analysis Issues,” dated August 1992, concluded that the Day- Night Average Sound Level (DNL) is the recommended metric and should continue to be used as the primary metric for aircraft noise exposure. However, DNL analysis may optionally be supplemented on a case-by-case basis to characterize specific noise effects. Because of the diversity of situations, the variety of supplemental metrics available, and the limitations of individual supplemental metrics, the FICON report concluded that the use of supplemental metrics to analyze noise should remain at the discretion of individual agencies.
FAA uses Ldn = 65 dB as a boundary for determining a significant noise impact with respect to an exposure-response curve which relates DNL to a nominal percentage of the population that is predicted to be "Highly Annoyed". The percent of the population predicted by the 1992 FICON curve to be highly annoyed at this exposure level is 12.3%.
Lesson’s learned:
Federal Policies and Procedures need to be reviewed and up-dated in regard to the FAA standard currently being used to measure air traffic noise pollution. NextGen is the way of the future but the fuel saving benefit to the aviation industry can not out-weight the negative impacts PBN is having on the environment when it is improperly implemented.
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