FAA Noise Control and Regulations

In the 1960's commercial jet aircraft were 6 times louder than the ones used today. Due to the noise problems caused by these aircraft. People such as Lighthill and Goldstein began to do research in acoustic theory dealing specifically with jet engine noise. Since 1976 the research done to improve jet engines in conjunction with new noise regulations introduced by the FAA, the number of people exposed to noise levels above 65 dB has dropped from about 7 million to only 500,000.

Since 1976 when the FAA first started regulating commercial aircraft noise, major efforts have been underway to make aircraft quieter without substantial loss of power. One of the major contributors to the great decline in jet exhaust noise was the widespread use of the turbofan engine. However as the bypass ratio continued to increase, fan noise became an increasingly dominant source of noise. As efforts continue to develop new methods of reducing engine noise, additional effort is being put into area such as creating flight paths around highly populated areas, phasing out older designs of aircraft such as phase 1 and phase 2, and passing zoning laws to limit residential use of land around airports. Below is a list of the FAA's current goals to continue to reduce the noise footprint around airports and Figure F1 below shows the effect a 6 dB noise reduction would have on the noise footprint of a major airport.
Current FAA Goals
  • Continue to reduce aircraft noise by phasing out stage one and two aircraft
  • Use new technology to reduce noise impact
  • Encourage zoning efforts to ensure compatible usage of land around airports to minimize disturbances
  • Provide special consideration for national parks and reserves
  • Look further into the design of new flight paths away from highly populated areas
  • Ensure strong financial support for noise control projects and research
Figure F1: fade from black to gray shows the reduction of people annoyed by aircraft noise for a noise reduction of 6 dB
In order for the FAA to enforce the regulations currently in place, a standard of measurement had to be implemented so that sound levels could be consistently monitored. Figure F2 below shows a diagram of how this measurement is taken. From this diagram, it can be seen that the approach passes much closer to the microphone coming in for landing at only three degrees, while the takeoff requires no more than ten degrees until reaching the cutback where the plane reaches cruising altitude and can cut back the thrust on the engines. For this reason the faster a commercial aircraft can climb the lower its sound level will appear. Distances from the startpoint to the cutback and from start until the microphones are also provided as standard to ensure consistent measurements.
Figure F2: diagram of standard distances and flight paths for measuring takeoff and landing noise levels of commercial aircraft.