• What is noise?
  • Noise is unwanted sound; what is music to music to one may be noise to another
  • By its very nature noise is subjective
  • Noise cannot be measured, only sound can be measured
• Sound pressure ranges are very large, therefore expressed on a logarithmic scale
• Logarithmic scale compresses the wide range in sound pressures to a more useable range
• Standard unit of measurement is the decibel (dB), which is the basis for aircraft noise analysis

The following is a graph of Sounds Environs:

The chart below shows noise levels for common sounds found indoors and outdoors:

• Sound levels decrease primarily as a function of:
  • Distance from source
  • Atmospheric absorption
  • Ground attenuation
• Overall, atmospheric conditions play a significant role in affecting the sound levels on a daily basis and how these sounds are perceived by the public.
• The atmosphere can absorb sound depending on the temperature of the air and humidity levels
  • Less sound will be absorbed by the atmosphere on days with high humidity and high temperatures
  • Temperature inversions (or cloud cover) can cause the sound to reflect back to the ground
• Ground absorption is important to the study of noise from airfield operations
  • Closer the source of the noise is to the ground, the more the sound will be  attenuated by the ground
  • Soft surfaces, such as vegetation, absorb more sound than hard surfaces like water

• Noise exposure can be quantified using measurements or modeling
• Measuring sound levels will accurately tell us:
  • The sound levels at a specific location for the time period measurements were made
  • Historical record of the sound levels at a specific location
  • Historical trends; but measurements do not predict future noise levels
• Modeling sound exposure accurately tells us the sound levels
  • Over broad geographic areas as well as at specific locations for a specific time period
  • Modeling can produce a historical record
  • Modeling can be predictive by showing expected trend

• Management of aircraft noise falls primarily into two categories:
  • Aircraft Operational procedures—Abatement
  • Land use measures—Mitigation
• Extent of available Noise Abatement programs varies based on the extent and complexity of the noise concerns at the airport
• Programs should be safe, cost effective, and capable of being implemented to be successful
• Examples include:
  • Preferential runway use program
  • Modify approach and departure procedures
  • Limit operations, such as touch-and-go operations
  • Designated traffic patterns
• Noise mitigation refers to measures that address existing and future non-compatible land uses in the vicinity of airports
• Examples of noise mitigation include:
  • Airport Land Use Compatibility Plan
  • Sound insulation
  • Zoning/building codes

• Federal law sets aircraft noise standards, prescribes operating rules, establishes the compatibility planning process, and impedes the airport proprietor from implementing operational restrictions
• State law sets forth compatibility planning guidelines and noise standards but exempts aircraft in flight
• Local noise ordinances set noise standards and provide for compatible land use planning but exempt aircraft in flight

Federal Law Preempts State and Local Regulations Pursuant to Aircraft in Flight