. When the Memphis Municipal Airport opened in the 1920’s, it was seven miles from downtown. Yet, American and Chicago and Southern Airlines operated from grass strips surrounded by farmland. Over the years, the airport grew as Memphis grew. Grass strips gave way to concrete. Farm hangars were replaced with a proper terminal. The radial throb of DC-7’s and Super Connies disappeared and were replaced with the scream of turbojets from 707’s and DC-8’s. The airport, which was once on the outskirts of town, was now surrounded by suburban neighborhoods. People who bought houses near a small airport in the 1950s and '60s had no idea that soon, its largest tenant FedEx, would make the airport the busiest in the world between 10 pm and 3 am. People living near the airport began complaining about a whole range of discordant sounds, from the banshee wail of taxing jets to the ceiling shaking thunder of the engines on takeoff. Noise pollution became an unfortunate side effect of the jet age.

The U.S. began enacting legislative controls with the Aircraft Noise Abatement Act in 1968. This authorized the FAA to prescribe standards for the measurement of aircraft noise. This act was later modified by the Noise Control Act of 1972 which now required consultation with the Environmental Protection Agency (EPA). "The Congress declares that it is the policy of the United States to promote an environment for all Americans free from noise that jeopardizes their health or welfare" (Noise Control Act of 1972). Other federal programs provided money for noise reduction projects such as sound proofing nearby buildings to include homes and schools, and land acquisition to acquire homes surrounding airport property and relocating them to quieter locations (Government Accountability Office, [GAO], 2001). Land use guidelines and zoning laws addressed land use in the vicinity of the airport. They idea behind land use planning is that residential development should not occur in areas near airports exceeding a described decibel level, as well as limiting airport expansion in existing residential areas.

Additional acts required aircraft designers and manufactures to follow FAA Aircraft Certification standards to achieve noise reduction. These standards were classified as “stages” with early aircraft classified as stage 1. These stages were based on noise limits according to aircraft type (jet, propeller, and helicopter), weight, and number of engines. For an aircraft to be certified for airworthiness, it needed to comply with the appropriate stage. As aircraft noise reduction technology improved, more stringent noise standards were put in place and lower stage aircraft needed to be modified to met the new standard or be phased out (Federal Registrar, 2003).

The metrics used in aircraft noise certification is the Effective Perceived Noise (EPNdB). “EPNdB is a measure of human annoyance to aircraft noise which has special spectral characteristics and persistence of sounds. It accounts for human response to spectral shape, intensity, tonal content and duration of noise from an aircraft” (Depitre, 2006). Approach measurement points are located 200 meters from runway threshold. Flyover measurement points are 6500 meters from the runway threshold. Laterally, they are measured 450 meters off runway centerline (Depitre, 2006).

By 1999, all stage 2 aircraft were phased out of use in the United States followed by Europe in 2002. Some older stage 2 aircraft met stage 3 compliance by installing noise reduction technology called “hush kits” but the greater reduction in noise was because newer aircraft such as the 757 and 767 were generally quieter than the aircraft they were replacing (GAO, 2001) The FAA currently has standards up to stage 4 but the international community is pushing for more stringent standards which the FAA will be calling stage 5 to be effective 2017 (Federal Aviation Administration, 2013).

In an effort to further reduce noise exposure to the surrounding community, the Memphis Shelby County Airport Authority (MSCAA) initiated the 1987 Noise Compatibility / Property Acquisition Program. Approved by the FAA, this $120 million program purchased approximately 1,400 single family residences and several businesses located within a 75 decibel noise contour. Entire neighborhoods were bought and the housed leveled to produce a noise buffer surrounding the airport. Other plans targeted local zoning regulations and building codes to prevent development in noise sensitive areas (Memphis International Airport, 2014).

Despite the transition to quieter aircraft, and programs put in place to limit residential growth around the Memphis International Airport, community opposition to the airport’s noise continued. Area residents sued the MSCAA in 1987. The Airport Residence Alliance claimed the rapid growth of air traffic impaired their quality of life and reduced property values caused by noise and other forms of pollution. These residents were located outside the initial buyout area and wanted the airport to buy their property as well. Funds for the noise mitigation program by then had already been spent. The U.S. District Court for the Western District of Tennessee entered a final judgment in 1998 approving settlement on the case. The MSCAA made payments to 12,430 claimants with benefits to the settlement class estimated to be $22 million (Memphis International Airport, 2014). Payments would range from $500 to $4,200 depending on how long residents had lived there.

Because FedEx operates primarily between 10pm and 3am, they must be amenable to noise during their night time operations. Runway use is sensitive to the layout of the surrounding community and plays an important part in noise mitigation. Therefore, operations differ between day and night. Memphis has three north/south parallel runways and one east/west runway. During the day when there is primarily passenger traffic and few noise issues, ATC lands 36L, 36R and 27 and takeoff 36L and 36C. This pattern however requires longer taxi times for FedEx whose sorting facilities are on the north side of the airport. With the airport’s location south of Memphis, ATC directs aircraft south of the airport landing on runways 36 and taking off on 18 primarily. Not only does this mitigate noise issues, it greatly reduces taxi time for these time critical flights (Cosmas and Martini, 2007).

Local noise abatement procedures are as follows:

1. Engine run-ups may only be conducted from 6:00am to 10:00pm, in the designated run-up areas, except in emergency situations, and only after notification to the airport authority.

2. Turbojet aircraft shall not be authorized to turn nor assigned a heading which will result in an aircraft below altitude 3,000 traversing the residential areas north of Holmes Rd. E and east and west of the extended centerline of Runways 18 L/R.

3. Turbojet aircraft departing Runway 27 shall not be authorized to turn south until leaving 3.000 feet or two miles from the departure end of the runway.

(Memphis International Airport, 2014).

As cities expand and developments encroach closer to noisy airport environments, noise will continue to be a major concern for communities surrounding airports. This concern continues despite the fact that there have been considerable improvements in aircraft technology to reduce engine noise, and controls put in place to limit the population exposed to it. Memphis International Airport and FedEx have realized that proper noise mitigation efforts make financial sense as well being a “good neighbor” providing a better quality of life for their surrounding communities.

References

Cosmas, A., Martini, B. (December 14, 2007). UPS and FedEx Hubs: Comparing Louisville and Memphis Cargo Hub Operations. Retrieved from http://ardent.mit.edu/airports/ ASP_exercises/ASP%20matl%20for%20posting%202007/UPS%20and%20FedEx%20Hub%20Operations%20Cosmas%20Martini

Depitre, A. (2006). Noise Certification Workshop. Retrieved from http://www.icao.int/ Meetings/EnvironmentalWorkshops/Documents/Noise-Certification-Workshop-2006/Depitre_4.pdf

Federal Aviation Administration. (2013). Details on FAA Noise Levels, Stages, and Phaseouts. Retrieved from https://www.faa.gov/about/office_org/headquarters_offices/apl/noise _emissions/airport_aircraft_noise_issues/levels/

Federal Registrar. Vol. 68, No. 230. (December 1, 2003). Stage 4 Aircraft Noise Standards. Department of Transportation. Federal Aviation Administration. 14 CFR Parts 36 and 91. Retrieved from http://www.gpo.gov/fdsys/pkg/FR-2003-12-01/pdf/03-29147.pdf

Government Accountability Office. (September, 2001). Aviation and the Environment. Transition to Quieter Aircraft Occurred as Planned, but Concerns About Noise Persist. (GAO Publication No. 01-1053). Washington, D.C.: U.S. Government Printing Office.

Memphis International Airport. (2014). Part 150 Study Update. Noise Exposure Maps and Supporting Documentation.