Abandon the Current Day-Night Level Noise Standard of 65 dBA DNL
"A punch from Michael Tyson, averaged over an hour, is equivalent to a love pat." Averaging hides the impact.
The FAA uses 65 dBA DNL to determine the onset of substantial impact. In reality, substantial impacts occur to millions of people well below the 65 decibel level. This value is inadaquate for several reasons. From a scientific perspective, it is not supported by research. The 65 decibel level is derived from the Schultz Curve, which correlated people reporting being highly annoyed by noise with noise levels. Substantial impact occurs well before people become highly annoyed. In addition, the data used in the Shultz Curve for airports shows that "highly annoyed" occurs around 57 decibels, not 65 (Journal of the Acoustical Society of America, Dec. 1998, 3432).
The EPA had identified 55 dBA DNL as a more appropriate noise level. The 55 dBA DNL value, while being more in line with recent reexaminations of the Schultz curve, remains inadequate for two reasons that have more to do with the metrics, or noise descriptors, than a particular value.
1) Using dBA or the A scale does not adequately account for low frequency noise. The "A" weighting discounts low frequency noise by 40 or more decibels. A standard that accounts for low frequency noise using the C weighting is necessary to reflect the impact of low frequency noise, such as 65 dBC DNL.
2) The DNL refers to a day-night level, a yearly average. Averages, however, do not adequately account for the impacts of aircraft noise on individuals. Averages understate "single events" and it is these single loud noises as the airplanes fly overhead that can disrupt sleep and adversely impact an individual's well-being. Being awakened at 6 a.m. and not getting a full night's sleep can negatively affect the individual's activities throughout the day - at work, traveling, and at home. Loud "single noise events" also intrude on conversations, television viewing, reading, and speaking on the telephone. These "single events" rob people of a decent quality of life and potentially could have lasting health effects. Most communities restrict single events to 55-65 dBA in residential areas. A 75 dBC maximum corresponds to the upper end of that range.
Please write to the FAA and tell them to:
Send comments in triplicate to:
Federal Aviation Administration
Office of the Chief Counsel
Attention: Rules Docket (AGC-200)
Docket No. 
800 Independence Avenue, SW
Washington, DC 20591
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