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A-Weighted Sound (dBA) -
A-weighted decibels adjust sound pressure towards the frequency range
of human hearing.
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Above Ground Level (AGL) -
The height of an aircraft above the surface of the earth.
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Advanced Flight
Track Procedures (AFTPro) - AFTPro will utilize existing Area
Navigation (RNAV) technology enabling aircraft to adhere to a track
over the ground with greater precision. The procedures developed
follow the preferential nighttime flight tracks that were designed to
navigate aircraft towards areas of more compatible land use, such as
forest preserves, highway corridors and industrial areas. The use of
this technology will automatically compensate for wind drift and air
speed while ensuring airspace safety, efficiency and, when possible,
minimizing the noise impacts to surrounding residences.
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Air Route Traffic
Control Center (ARTCC) - An FAA facility established to provide
air traffic control service to aircraft operating on an Instrument
Flight Rules (IFR) flight plan within controlled airspace during the
en route portion of a flight.
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Air Traffic Control (ATC) -
A service operated by appropriate authority to promote the safe,
orderly, and expeditious flow of air traffic.
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Airport Improvement Program
(AIP) - A Federal funding program for airport improvements. Funds are
derived from sources such as airline tickets, aviation fuel, etc.
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Airport Noise
Monitoring System (ANMS) - The Chicago Airport System's Airport
Noise Monitoring System is a comprehensive system to provide actual
measurement of the aircraft noise levels in Chicago neighborhoods and
suburban communities around O'Hare and Midway. This integrated system
includes many components, including a network of permanent noise
monitors that measure the noise environment and a system directly
connected to the FAA's air traffic control radar that collects
aircraft flight tracks.
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Air Traffic Control Tower (ATCT)
- The air traffic control facility located on an airport and
responsible for traffic separation within the immediate vicinity of an
airport as well as on the surface of the airport.
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Ambient Noise - The totality of
noise in a given place and time; usually a composite of sounds from
varying sources at varying distances.
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Day-Night Average Sound
Level (DNL) - A noise measure used to describe average aircraft
noise levels over a 24-hour period, typically an average day over the
course of a year. DNL penalizes aircraft operations that occur between
the hours of 10 p.m. and 7 a.m. by 10 decibels to account for
increased annoyance when ambient noise levels are lower and people are
trying to sleep. DNL may be determined for individual locations or
expressed in noise contours. DNL is currently the accepted measure for
aircraft noise analysis.
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Decibel (dB) - Sound is measured by
its pressure or energy in terms of decibels. The decibel scale is
logarithmic; when the scale goes up by ten, the perceived sound is two
times as loud.
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Delay - The difference, in minutes,
between the scheduled time and actual time of an aircraft arrival or
departure. For airport planning purposes, it is often expressed as an
annual average delay per aircraft operation (in minutes).
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Federal Aviation
Administration (FAA) - The Federal Agency responsible for insuring
the safe and efficient use of the Nation's airspace, for fostering
civil aeronautics and air commerce, and for supporting the
requirements of national defense. The activities required to carry out
these responsibilities include: safety regulations; airspace
management and the establishment, operation, and maintenance of a
system of air traffic control and navigation facilities; research and
development in support of the fostering of a national system of
airports, promulgation of standards and specifications for civil
airports, and administration of Federal grants-in-aid for developing
public airports; various joint and cooperative activities with the
Department of Defense; and technical assistance (under State
Department auspices) to other countries.
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Federal Aviation
Regulations (FAR) - The body of Federal regulations relating to
aviation. Published as Title 14 of the Code of Federal Regulations.
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Fixed Threshold - Static
baseline noise level above which microphones measure a noise event.
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Flight Track Utilization
- The use of established routes for arrival and departure by aircraft
to and from the existing runways at the airport.
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Fleet Mix - The mix or differing
types of aircraft operating in a particular environment.
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Floating Threshold -
Baseline noise level determined by current ambient noise level, above
which microphones measure a noise event.
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Fly Quiet Program - The use of
designated noise abatement flight procedures to further reduce the
impact of aircraft noise. The Fly Quiet Program provides comprehensive
guidance for pilots to use designated quiet flight and operating
procedures developed by the Department of Aviation in cooperation with
the O'Hare and Midway Noise Compatibility Commissions, the airlines,
and Air Traffic Controllers. The Chicago Department of Aviation
distributes Fly Quiet Aviator's Manuals to airline pilots and air
traffic controllers that contain information on preferred runways and
flight tracks which route aircraft over the least populated areas --
such as forest preserves, highways, as well as commercial and
industrial areas.
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Ground Run-up Enclosure (GRE)
- The GRE at O'Hare uses acoustical dampening principles to reduce the
noise impacts of aircraft engine ground run-ups. Aircraft ground
run-ups are routine aircraft engine maintenance tests that require the
operation of an engine at high power for extended periods of time
generating continuous elevated noise levels. The GRE at O'Hare is
located adjacent to the airline maintenance area, and is oriented to
direct aircraft noise toward the center of the Airport and terminal
core.
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Ground Track - The seeming path an
aircraft would follow on the ground if its airborne flight path were
plotted on the terrain.
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Hushkit - An aircraft-engine quieting
device added to aircraft engines originally certified as Stage 2 in
order to meet more stringent Stage 3 standards.
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ISIS (Interactive Sound Information
System) - PC-based program that provides users with interactive noise
level demonstrations, such as audio comparisons of aircraft decibel
levels as experienced indoors versus outdoors.
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Instrument Approach - A
series of predetermined maneuvers for the orderly transfer of an
aircraft under instrument flight conditions from the beginning of the
initial approach to a landing, or to a point from which a landing may
be made visually.
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Instrument Flight Rules
(IFR) - That portion of the Federal Air Regulations (14 CFR 91)
specifying the procedures to be used by aircraft during flight in
Instrument Meteorological Conditions.
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Instrument Landing System
(ILS) - An electronic system installed at some airports that helps to
guide pilots to runways for landing during periods of limited
visibility or adverse weather.
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Instrument
Meteorological Conditions (IMC) - Weather conditions expressed in
terms of visibility, distance from clouds, and cloud ceilings during
which all aircraft are required to operate using instrument flight
rules (IFR).
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Integrated Noise Model (INM)
- A computer model developed, updated and maintained by the FAA to
predict the noise impacts generated by aircraft operations.
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Land Use Compatibility -
The ability of land uses surrounding the airport to coexist with
airport-related activities with minimum conflict.
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Ldn - (See DNL).
Ldn is used in place for DNL in mathematical equations only.
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Leq - Equivalent Sound Level. The steady
A-weighted sound level over any specified period (not necessarily 24
hours) that has the same acoustic energy as the fluctuating noise
during that period (with no consideration of nighttime weighting). It
is a measure of cumulative acoustical energy. Because the time
interval may vary, it should be specified by a subscript (such as Leq8
for an 8-hour exposure to noise) or be clearly understood from the
context.
Linked Event - Noise
events, complaints, operations and flight tracks that have been matched
together by time proximity. Complaints can only be linked to noise
events that have been already linked to an operation.
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Mean Sea Level (MSL) - The
average height of the surface of the sea for all stages of the tide,
used as a reference for elevations. Also called sea level datum.
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Noise - Unwanted sound.
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Noise Abatement - A measure or
action that minimizes the amount or impact of noise on the environs of
an airport. Noise abatement measures include aircraft operating
procedures and use or disuse of certain runways or flight tracks.
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Noise Contour Map - A map
representing average annual noise levels summarized by lines
connecting points of equal noise exposure.
Noise Event - When
noise at a microphone exceeds a threshold for a specific length of time.
NOTAM
- Notice to Airmen - A notice containing information
concerning the establishment, condition, or change in any component
(facility, service, or procedure of, or hazard in the National Airspace
System) and the timely knowledge of which is essential to personnel
concerned with flight operations.
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Operation - A take-off or a landing.
Every flight requires two operations, a take-off and a landing.
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Outer Marker (OM) - An ILS
navigation facility in the terminal area navigation system located
four to seven miles from the runway edge on the extended centerline
indicating to the pilot that he/she is passing over the facility and
can begin final approach.
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Part 150 - Established
by Congress under the Aviation Safety and Noise Abatement Act of
1979 for the purpose of developing a balanced and cost effective
program to reduce the effects of aircraft noise on local
communities.
Passenger Facility Charge (PFC)
- A charge covered by Federal Aviation Regulation Part 158, which is
imposed by a public agency on passengers enplaned at a commercial
service airport it controls.
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Remote
Monitoring Terminal (RMT) - A remote device with a microphone and
data processing storage unite that is used to record noise events.
Run-Up - A routine procedure for testing
an aircraft engine at a high power setting. Engine run-ups are
normally conducted by airline maintenance personnel checking an
aircraft engine or other on board system following maintenance.
RNAV -
RNAV stands for Area Navigation. RNAV is a method of navigation
which permits aircraft operations on any desired flight path within the
coverage of station referenced navigation aids or the limits of the
capability of self-contained aids, or any combination thereof. Airborne
RNAV equipment automatically determines aircraft position by processing
data from one or more sensors and guides the aircraft in accordance with
appropriate routing instructions. Additional navigation parameters such
as distance and bearing to a pre-selected waypoint can also be computed
from the aircraft position and the location of the waypoint, depending
upon the capability of the RNAV equipment. Position can be displayed to
the pilot in various ways, most practically in terms of the aircraft
position relative to the pre-computed desired track. Most RNA equipment
can employ any lateral displacement of the aircraft from the desired
track to generate track guidance signals to the autopilot. With other
less sophisticated RNAV equipment the pilot takes manual corrective
action.
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Single Event - An occurrence of
audible noise, usually above a specified minimum noise level, caused
by an intrusive source such as an aircraft overflight, passing train
or ship's horn.
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Sound - Sound is the result of a sound
source vibration in the air. The vibration produces alternating bands
of relatively dense and sparse particles of air, spreading outward
from the source in the same way as ripples do on water after a stone
is thrown into it. The result of the movement is fluctuation in the
normal atmospheric pressure or sound waves.
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Sound Exposure Level (SEL)
- A measure of the physical energy of the noise event that takes into
account both intensity and duration. Expressed in decibels (dB).
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Stage 2 Aircraft - Aircraft
that meet the noise levels prescribed by FAR Part 36 and are less
stringent than those established for the quieter designation (Stage
3). The Airport Noise and Capacity Act required the phase-out of all
Stage 2 aircraft over 75,000 pounds by December 31, 1999.
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Stage 3 Aircraft - Aircraft
that meet the most stringent noise levels set in FAR Part 36.
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Standard
Instrument Departure Procedure (SID) - A planned IFR air traffic
control departure procedure printed for pilot use in graphic and/or
textual form. SID's provide transition from the terminal to the en
route air control structure.
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Standard Terminal
Arrival Route (STAR) - A planned IFR air traffic control arrival
procedure printed for pilot use in graphic and/or textual form. STAR's
provide transition from the en route air traffic structure to an outer
fix or an instrument approach fix in the terminal area.
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Terminal Radar
Approach Control (TRACON) - An FAA air traffic control service to
aircraft arriving and departing or transiting airspace controlled by
the facility. The TRACON for the Chicago area is located in Elgin,
Illinois.
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VOR (Very
High Frequency Omni Directional Range) – A ground based electronic
navigation aid transmitting very high frequency navigation signals, 360
degrees in azimuth, oriented from magnetic north. Used as the bases for
navigation in the National Airspace System.
Visual Approach - An approach
conducted on an IFR flight plan that authorizes the pilot to proceed
visually and clear of clouds to the airport.
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Visual Flight Rules (VFR) -
Rules and procedures specified in 14 CFR 91 for aircraft operations
under visual conditions.
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Visual
Meteorological Conditions (VMC) - Weather conditions expressed in
terms of visibility, distance from cloud, and cloud ceiling equal to
or greater than those specified in 14 CFR 91.155 for aircraft
operations under Visual Flight Rules (VFR).
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