Boston Logan Airport Noise Study
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RADAR - A device that, by measuring the time interval between transmission and reception of radio pulses and correlating the angular orientation of the radiated antenna beam or beams in azimuth and/or elevation, provides information on range, azimuth, and/or elevation of objects in the path of the transmitted pulses.


RECORD OF DECISION (ROD)- A document prepared in association with an Environmental Impact Statement/Report (EIS/EIR) that provides a concise public record of the decision made by the sponsoring agency on a proposed action for which an EIS/EIR was prepared. The ROD identifies the alternatives considered in the EIS/EIR, whether all practicable means to avoid or minimize environmental harm have been adopted, and if not, why they were not.

RELIEVER AIRPORT - An airport accommodating general aviation aircraft operations that might otherwise have to be accommodated at a congested air carrier airport.

REQUIRED NAVIGATION PERFORMANCE (RNP) - RNP applies to navigation performance within an airspace. is intended to characterize an airspace through a statement of the navigation performance accuracy (RNP type) to be achieved within the airspace. The RNP type is based on a navigation performance accuracy value that is expected to be achieved at least 95 percent of the time by the population of aircraft operating within the airspace. Most aircraft operating in the RNP environment carry some type of RNAV equipment. RNAV operations within the RNP concept permit flight in an airspace within prescribed accuracy tolerances without the need to fly directly over ground based navigation facilities

RETROFIT - The retroactive modification of existing jet aircraft engines for noise reduction purposes.

RUNWAY – A defined rectangular area on an airport for the purpose of landing and taking off of aircraft. Runways are numbered in relation to their magnetic direction, rounded to the nearest 10 degrees (i.e., Runway 14, Runway 32).


RUNWAY OBJECT FREE AREA - The runway object free area (OFA) is a two dimensional ground area surrounding the runway. The runway OFA clearing standard precludes parked aircraft and objects, except objects whose location is fixed by function.

RUNWAY PROTECTION ZONE (RPZ) - The RPZ (formerly referred to as the runway clear zone) is trapezoidal in shape and centered about the extended runway centerline. It begins 200 feet beyond the end of the area usable for takeoff or landing. Displacing the threshold does not change the beginning point of the RPZ unless declared runway distances have been established by the airport sponsor and approved by the FAA. The RPZ dimensions are functions of the design aircraft, type of operation, and visibility minimums.

RUNWAY THRESHOLD - The beginning of that portion of a runway usable for landing.


SEVERE NOISE EXPOSURE - Exposure to aircraft noise that is likely to interfere with human activity in noise-sensitive areas -repeated vigorous complaints can be expected and group action is probable. This exposure may be specified by a cumulative noise descriptor as a level of noise exposure, such as DNL 75. (See SIGNIFICANT NOISE EXPOSURE.)

SHIELDING - The attenuation of a sound by placing walls, buildings, plants, or other barriers between a sound source and the receiver. Also used with light to minimize impacts by introducing manmade or natural elements to reduce or eliminate glare.

SIGNIFICANT EFFECT ON THE ENVIRONMENT - A substantial, or potentially substantial, adverse change in any of the physical conditions within the area affected by the project, including land, air, water, minerals, flora, fauna, ambient noise, and objects of historic or aesthetic significance. An economic or social change by itself is not considered a significant effect on the environment. However, a social or economic change that is related to a physical change may be considered in determining whether a physical change is significant.

SIGNIFICANT NOISE EXPOSURE - Exposure to aircraft noise that is likely to interfere with human activity in noise sensitive areas; individual complaints may be expected and group action is possible. This exposure may be specified by a cumulative noise descriptor as a level of noise exposure, such as DNL 65. (See SEVERE NOISE EXPOSURE.)

SINGLE EVENT - Noise generated by a single event, such as a single aircraft flyover.

SOUND EXPOSURE LEVEL (SEL) - SEL is a time-integrated measure, expressed in decibels, of the sound energy of a single noise event. The sound level is integrated over the period that the level exceeds a threshold (normally 65 dBA for aircraft noise events). Therefore, SEL accounts for the duration of the sound. SELs for aircraft noise events depend on the location of the aircraft, the type of operation (landing, takeoff, or overflight), and the type of aircraft.

SLANT RANGE- The line-of-sight distance between two points, not at the same level relative to a specific datum.

Slant Range

SOUND INSULATION - (1) The use of structures and materials designed to reduce the transmission of sound from one room or area to another, or from the exterior to the interior of a building.
(2) The degree of reduction in sound transmission, or noise level reduction (see also), by means of sound-insulating structures and materials.

SOUND LEVEL (NOISE LEVEL) - The weighted sound pressure level obtained by the use of a sound level meter having a standard frequency filter for attenuating part of the sound spectrum.

SOUND LEVEL METER - An instrument consisting of a microphone, an amplifier, an output meter, and frequency weighting networks used to measure noise and sound levels in a specified manner.

STANDARD TERMINAL ARRIVAL ROUTE (STAR) - A preplanned and published instrumental arrival route.


TERPS - Certain airspace needs to be cleared for aircraft operations. This airspace is determined by the application of operating rules and terminal instrument procedures (TERPS). Removing obstructions to air navigation, except those that an FAA aeronautical analysis determined need not be removed, satisfies these requirements. Subpart C of FAR Part 77 defines obstructions to air navigation. (See FAA HANDBOOK 8260.3B.)

TERMINAL RADAR APPROACH CONTROL (TRACON) - Radar approach facility for an airport.

TIME ABOVE (TA) - A metric that shows the total amount of time that aircraft noise levels exceed a specific continual sound level threshold. TA is expressed in minutes, calculated to the nearest minute.


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