Abbreviations and Acronyms

AGL -- Above Ground Level
ARFF -- Airport Rescue and Fire Fighting Facility
ATC -- Air Traffic Control
ATCT -- Air Traffic Control Tower
dB -- Decibel
DNL or LDN -- Day-Night Average Sound Level
DOA -- Department of Aviation
FAA -- Federal Aviation Administration
FAF -- Final Approach Fix
FAR -- Federal Aviation Regulation
ft. -- Feet
FPM -- Feet Per Minute
IFR -- Instrument Flight Rules
KIAS -- Knots Indicated Airspeed
MDW -- Chicago Midway Airport
MSL -- Mean Sea Level
NAVAIDS -- Navigational Aids
ORD -- Chicago O'Hare International Airport
Part 150 -- FAR Part 150 Noise Compatibility Planning Process
VFR -- Visual Flight Rules
VOR -- Very High Frequency Onmidirectional Range
VORTAC -- VHF Onmidirectional Range with Tactical Air Navigation
V2 -- Takeoff Safety Speed
Vs -- Stalling Speed
Vfs -- Final Segment Speed

Glossary of Terms

Day-Night Average Sound Level (DNL)

A noise measurement used to describe the 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. an additional 10 decibels to account for increased sensitivity to nighttime noise. DNL may be determined for individual locations or expressed contours. DNL is currently the accepted measurement for aircraft noise analysis.

Decibel (dB)

A unit of relative loudness. The smallest amount of change that can be detected by the human ear is one decibel. A 20 decibel sound is 10 times as loud as a 10 decibel sound; a 30 decibel sound is 100 times as loud.

Federal Aviation Regulation (FAR)

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.

Land Use Compatibility

The ability of land uses surrounding the airport to coexist with airport-related activities with minimum conflict.