V. Airport and Local Land Use Planning Processes
measures were implemented. This understanding can serve as a basis for
considering the applicability and ultimate selection and implementation of noise
controls as they relate to specific airports. However, measures right for the
environs around one airport may not be right at another. Thus, this guide does not
recommend specific controls for implementation but, instead, identifies a wide
variety of possible noise control methods related to aircraft flight procedures and
land use controls, which could be applied for specific airport conditions.
This discussion of FAR Part 150 Noise Compatibility Programs is designed to
provide an understanding of the federal process available to airport owners to
mitigate the impacts of aircraft noise on surrounding communities. Through this
process, airport owners work with the FAA, airport tenants and users, local and
regional planning agencies, local units of government, and other interested parties
to identify mitigation measures which can be implemented through airport
operations, air traffic control measures, and land use planning and regulatory
actions. Participation in this program is voluntary for the airport owner.
When an airport owner conducts a Part 150 Noise Compatibility Program
planning study, it is advisable to consider a threshold of annual aircraft activity at
the airport must be met. This threshold is defined in FAA Order 5050.4A, Airport
Environmental Handbook, October 8, 1985, paragraph 47 (e)(1):
No noise analysis is needed for proposals involving Design Group
I and II airplanes on utility (reference Advisory Circular 150/5300
4B) or transport (reference Advisory Circular 150/5300 12) type
airports whose forecast operations in the period covered by the
environmental assessment do not exceed 90,000 annual propeller
operations or 700 annual jet operations. These numbers of
propeller aircraft operations result in cumulative noise levels not
exceeding 60 Day/Night Level (DNL
1
) more than 5,500 feet from
start of takeoff roll or 65 DNL on the runway itself. Jet operations
of 700 or less do not produce a 60 DNL contour using this method.
Note that the Cessna Citation 500, the Gates Learjet 35A, and any
1
The noise emanating from airport operations rises, falls, and even ceases throughout the day. Various noise descriptors or metrics have been developed to reflect how people
are affected by the time-varying noise exposure levels resulting from aircraft operations. The Day-Night Average Sound Level (DNL) metric is currently the standard noise
descriptor specified by the Federal government for transportation noise sources. FAA Order 1050.1D, Policies and Procedures for Considering Environmental Impacts, and
Order 5050.4A, Airport Environmental Handbook, require the use of the DNL noise metric in evaluating noise exposure in environmental assessments of Federal actions. Part
150 of the Federal Aviation Regulations (FAR) specifies the use of DNL in noise compatibility studies.
The DNL metric employs the equivalent sound level (Leq), a single numerical noise rating which, over a given period of time, would represent the same noise energy as the
time-varying sound level. The DNL metric was derived to account for the greater annoyance caused by sound intrusion at night. It augments the equivalent sound level
occurring between 10:00 p.m. and 7:00 a.m. by 10 dB before being combined with the equivalent sound level for the period 7:00 a.m. to 10:00 p.m. The DNL provides a
numerical description of the weighted 24-hour cumulative noise energy level using the A-weighted decibel scale, typically over a period of a year. The method of weighting the
frequency spectrum, the A-weighted scale, was adopted by the FAA to describe environmental noise because it most closely mimics the receptivity of the human ear.
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