Noise Information

CITY OFATLANTA— DEPARTMENT OF AVIATION

Special Points

of Interest:

• Noise Mitigation

• History

• Frequently Asked Questions

• Facts

• Trends

• Roles & Responsibilities

We’re on the web at:

www.atlanta-airport.com

For More

Information

Please call Gail

Feltman, NOMS

(Noise & Operations

Monitoring System)

Analyst at 

(404) 209-2955.

To share a noise 

concern, please call 

(770) 43- NOISE

City of Atlanta — Department of Aviation

P.O. Box 20509

Atrium Suite 430

Atlanta, Georgia 30320

404-530-6600

Revised on 10/19/06

Aircraft

Hartsfield-Jackson Atlanta

International Airport
Frequently asked questions

What is a DNL?

DNL (Day-Night Sound Level) is based on sound levels measured in relative intensity of

sound, or decibels (dB), on the “A” weighted scale (dBA). This scale most closely approximates

the response characteristics of the human ear to sound. The higher the number, the louder the

sound. DNL represents noise exposure events over a 24-hour period. To account for human

sensitivity to noise between the hours of 10:00 pm and 7:00 am, noise events occurring during

these hours receive a “penalty” when the DNL is calculated. Each event is measured as if ten

events occurred. 

Noise Information

Aircraft

History of Noise Mitigation Efforts

The noise abatement/mitigation program at H-JAIA (Hartsfield-Jackson Atlanta International

Airport) has been ongoing for almost 30 years. It started with the implementation of noise

abatement departure tracks in 1972. Mitigation efforts began in 1975 with the acquisition and

relocation of the Mountain View community in Clayton County, and continued in 1978 with

the initiation of the Airport Noise Abatement and Land Use Compatibility (ANALUC) study

sponsored by the City of Atlanta and surrounding jurisdictions. Completed in 1980, the

study’s results set the stage for aircraft operational controls and land use compatibility

planning for the Airport. When the federal government passed noise regulations in 

the early 1980's, Hartsfield started a formal Federal Aviation Regulation (FAR) Part 150

study. This study led to the establishment of the Airport Noise Mitigation Program,

which continues today. Hartsfield's program is one of the oldest and most comprehensive airport noise abatement/mitigation programs in the United States.

What is NOMS?

NOMS is the acronym for a Noise and Operations Monitoring System. It consists of two

basic elements: (1) a direct-connect to the FAA’s radar system for the purpose of acquiring 

flight track information and (2) a geographic information system to correlate noise complaint

locations and flight tracks. The integration of these two systems allows the DOA to gather

information on the flight of aircraft over communities surrounding Hartsfield-Jackson 

Atlanta International Airport. 

Which is Quieter — An Arrival or Departure?

Arriving aircraft at low altitudes are generally quieter than departures of the same aircraft

type because this mode of flight requires much less engine power. However, close to the airport,

the relative “quietness” of an arrival may be offset by the fact that they are typically lower in altitude than departures over the same location. 

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To date, the program has resulted in:

The sound insulation of approximately 10,150 structures at a cost 

of about $174.5 million.

The relocation of residents, including the acquisition of over 2,720 

structures at a cost of about $177.7 million.

The establishment of procedures to control nighttime aircraft 

maintenance run-ups.

The installation of a permanent noise and operations monitoring 

system (NOMS) to provide the public information on Hartsfield-Jackson’s 

operations and address specific community concerns.
How Noise Levels are Determined

To more consistently and easily describe and compare noise environments comprised of

numerous single events, that vary in duration and magnitude over long periods of time, the

U.S. Environmental Protection Agency developed a single number descriptor. This descriptor

is the DNL, a noise metric which describes an average day/night sound level. DNL’s are used 

to quantify aircraft noise exposure in the vicinity of an airport. Noise contours of specific 

DNL levels are developed using the FAA’s Integrated Noise Model (INM). Airport specific

data used in the model to develop the contours results in the depiction of noise exposure

in the vicinity of an airport. Airport specific data used in the INM includes:

AVERAGE DAILY OPERATIONS - An aircraft operation is defined as an aircraft 

takeoff or an aircraft landing.

AIRCRAFT FLEET MIX - An aircraft fleet mix describes the types of aircraft using 

the airport. This data is important as some types of aircraft are noisier or quieter 

than others.

RUNWAY USE - Wind speed and direction are two primary factors that determine 

the direction of flow of aircraft using an airport’s runways.

FLIGHT CORRIDORS AND USAGE - Flight corridors describe concentrated areas 

of aircraft activity through which aircraft arrive and depart an airport.

DEPARTURE DESTINATIONS - Departure destinations are segregated into trip 

length categories corresponding to approximate flight distances. Aircraft traveling 

a long distance are usually heavier due to additional fuel requirements and are 

usually closer to the ground during climb-out than flights of shorter distance.

DAY/NIGHT USE - The percentage of operations during the day versus night is 

important as nighttime operations are penalized to account for the increased 

sensitivity of nearby residents to aircraft noise during these hours. 

Noise Contours

Noise contours are a series of lines superimposed on a map of the airport’s environs. These

lines represent various DNL levels (typically 65, 70, and 75 dBA). DNL noise contours are used

for several purposes:

Noise contours highlight existing or potential areas of significant aircraft noise

exposure (as defined by the FAA).

Noise contours are used to assess the relative aircraft noise exposure levels of

different runway and/or flight corridor alternatives.

Noise contours provide guidance to political jurisdictions in the development 

of land use control measures. These measures include zoning ordinances, 

subdivision regulations, building codes, and airport overlay zones.

It is the areas within the 65, 70, and 75 DNL noise contours that are considered by the FAA

to be the most impacted by aircraft-generated noise. Beyond the 65 DNL noise contour, noise

is most noticeable in areas below established flight corridors. 

The approved Hartsfield-Jackson Atlanta International Airport noise contours can be 

reviewed at the DOA’s office located at the Airport (404-209-2955).

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Roles and Responsibilities

The Aviation Noise Abatement Policy of 1976 summarized the key responsibilities of various

entities to control aircraft noise. 

THE FAA has the authority and responsibility to reduce aircraft noise at the source, implement

safe (and legal) noise abatement operational procedures which are recommended by the airport

proprietor, and encourage compatible land development.

AIRPORT PROPRIETORS are primarily responsible for planning and implementing actions that

manage the effects of aircraft noise within the airport’s environs. Such actions include noise

abatement ground procedures; land acquisition; acoustical treatments; other controls which do

not discriminate, create an unsafe situation, impede the management of the air navigation system,

or interfere with interstate or foreign commerce; and suggesting noise abatement operational

procedures.

STATE/LOCAL GOVERNMENTS AND PLANNING AGENCIES are responsible for compatible land

development through zoning, promulgating and enforcing building codes that incorporate

acoustically attenuating materials into edifices (especially residences), and disclosing the noise

impacts to their citizens.

AIR CARRIERS are responsible for retiring, replacing, and retrofitting older jets (per FAA regulations) and for flying aircraft in ways that minimize noise impacts on surrounding communities.

RESIDENTS AND PROSPECTIVE RESIDENTS in areas surrounding airports should strive to understand the noise problem and measures which can be taken to minimize the effect of noise.

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Noise Information

Aircraft

Aircraft Noise Trends

Today, more people than ever before are choosing aviation as their preferred method of

long distance transportation. Serving this demand, while managing aircraft noise within the 

airport’s environs, is a challenge for all airports proprietors.

Noise standards established by the FAA have already resulted in the replacement or

modification of what are known as Stage 1 and 2 aircraft (applies to aircraft over 75,000 lbs.

maximum take-off weight). FAR 91.805 mandated the phase-out of Stage 1 aircraft by January

1, 1985 and FAR 91.853 stipulated that only an airplane shown to comply with Stage 3 

standards could be operated post December 31, 1999. Because of the replacement of older, 

noisier jets with newer, quieter ones, and the improved climb capabilities of some Stage 3 

aircraft (the B757, the B767, and next-generation B737), airports have been able to 

continue to serve the growing demand for aircraft travel while the number of people

significantly impacted by aircraft noise has been reduced.

For More

Information

Please call Gail

Feltman, NOMS

(Noise & Operations

Monitoring System)

Analyst at 

(404) 209-2955.

To share a noise 

concern, please call 

(770) 43- NOISE