Noise 101

• 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