The most common complaint from those that live near airports concerns the excessive noise generated by jet aircraft as they take off and land. Many airports are located in or near high population centers, and the areas of the loudest noise may be located over houses, apartments, schools, museums, libraries, and other buildings where quiet is desired. Even if the airport was in an empty area when it was first built, expanding urban and suburban boundaries may result in noticeable noise pollution at some point in the future.
Aviation noise is a complicated issue both scientifically and politically. The science of noise is based on acoustics, which is an area of physics. Sound does not always work the way “common sense” would prescribe. For example, in the industrial noise arena it is possible for a sound to be very loud at a house two miles from the source while on the ground immediately beside the source it is not noticeable. This occurs because of two major factors: loudness relative to the environmental context, and propagation / reflection of sound waves (Postorino & Mantecchini, 2016). Other important factors include atmospheric absorption, diverging sound waves, and ground attenuation (SFO, 2015). The intensity of sound is measured in decibels, or dB. An interesting property of decibels is that the loudness doubles with each ten point increase in dB. Scientists who measure sounds such as aircraft noise do not examine the entire frequency range, since humans cannot hear all of the frequencies. Only frequencies between 20 Hz and about 15 kHz (depending on age) can be heard by humans. Therefore, the noise monitors used to measure aircraft noise filter the sound; this filtering is indicated by the abbreviation dBA (A-weighted sound pressure level).
Aviation noise can cause frustration and high emotions from both sides. Environmental Safety Associates, a company that provides consulting services for issues related to industrial noise and other environmental consequences, has established general guidelines for public reaction to noise levels. Their research showed that complaints were rare at 60 dBA, possible at 70 dBA, and likely at 80 dBA, while noise at the 90 dBA level typically resulted in letters of protest, local committee activities, and possible legal actions. By comparison, a vacuum cleaner at 10 ft. is about 70 dBA, a garbage disposal at 3 ft. is about 80, and a gas lawn mower at 3 ft. is approximately 90 dBA (SFO, 2015).
The Federal Aviation Administration provides standards for airport and aircraft noise limits. In the beginning, the standards focused on the aircraft themselves. They were grouped into four stages depending on the noise output of each type. The noisiest aircraft were Stage 1 and the quietest, Stage 4. Over time, the use of Stage 1 and Stage 2 aircraft were phased out. As of December 31, 2015, only Stage 3 and 4 aircraft were allowed to fly in the 48 contiguous states. When possible, air traffic controllers instruct pilots to use the runways and flight paths that will produce the least amount of noise, but weather and other hazards may make that impossible (FAA, 2016).
The final ruling, 14 Code of Federal Regulations (CFR) Part 150, Airport Noise Compatibility Planning, was established in 1985. The first steps in complying with the regulations involved mapping aircraft noise exposure around the airport and comparing it to current land use. As part of the first step, a noise exposure map report provides information about the noise contours around the runways and the usual flight paths. The report includes a current map and a 5-year predicted airport noise map. The second step involves determining the current use of land under the noise contours and finding ways to reduce the impact of current and projected noise levels. For example, Logan International Airport in Boston, Massachusetts, was one of the first airports to introduce standards related to noise. Because the entire area around the airport is urban, there was considerable overlap between noise contours and land use that was problematic. Several schools were subject to aircraft noise, so the airport authority paid for the schools to be soundproofed, thereby removing the problem.
San Francisco International Airport (SFO) is similar to Logan because the land around it is highly urbanized. The Airport Commission has been addressing community complaints about noise since the mid-1970s. In the early 80s, the first SFO 14 CFR Part 150 Noise and Land Use Compatibility Study was prepared, and a final version was FAA-approved in 1983. The SFO Noise Compatibility Program has been updated twice (1996 and 2002) and is due for another update. The Airport Commission has been working on the NEMs for 2014 and 2019; the noise contour in one area will be expanded significantly, and the Commission has identified land use in that area that is incompatible with the predicted noise levels. If the current land use (primarily residential) cannot be changed, the Commission recommended the addition of sound absorbing materials to reduce indoor noise to acceptable levels. This would be incorporated into building codes in the area. Federal funds are available to help property owners install soundproofing materials.
Overall, San Francisco International Airport has successfully dealt with its noise issues and continues to update its plans to stay ahead of citizen needs, rather than merely reacting. Their actions are examples that other airports can follow in addressing their own noise problems. I do not have any recommendations for improving their program.

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    References
  • Federal Aviation Administration (FAA). (2016). Aircraft noise issues. Retrieved from https://www.faa.gov/about/office_org/headquarters_offices/apl/noise_emissions/airport_aircraft_noise_issues/
  • Postorino, M. N., & Mantecchini, L. (2016). A systematic approach to assess the effectiveness of airport noise mitigation strategies.  Journal of Air Transport Management,  50, 71-82.
  • San Francisco International Airport (SFO). (2015). Noise exposure map report. Retrieved from http://www.flysfo.com/community-environment/noise-abatement/sfo-part-150-study/noise-exposure-map-report