News Article - September 28 2006

FAA noise pollution data may be misleading
  For candidates in the midterm elections this upcoming November, the effects of the Federal Aviation Administration’s proposals to modify flight patterns in Delaware County are a prominent concern. Recently, however, Associate Professor of Engineering Carr Everbach and Swarthmore Council Chairman Andrew Reilly raised doubts about the way in which the data was presented. Members of the Swarthmore Borough community have recently demonstrated apprehension over figures that implied that the FAA changes would result in noise increases of almost 1,000 percent. Although the increase in noise levels would still be a concern, it would not be nearly as dramatic. The original, core research was accurate; maps of the projected effects supported the conclusion that Delaware County would be detrimentally affected by planes flying lower and more often over the area. The discrepancy in the information, however, lies in the crucial distinction between two units of measure: the decibel and the sone.

   While the decibel is used to measure the relative difference in power or intensity, the sone is the unit of loudness as perceived by a person with normal hearing. Some people who examined the maps provided by the Delaware County Planning Department erroneously interpreted the projected increase in decibels as equivalent to a linear increase in noise level. Everbach said that although the data might have been difficult to interpret for some, it was not inaccurate. “The information is not incorrect as long as one says that the percent is a percentage in vibration,” he said. Everbach said that rather than see noise levels increase 1,000 percent, it would be reasonable to predict that the levels would double. As a result of this error in interpretation, many presumptions that had been made during the campaign have been rendered inaccurate. For example, the Borough of Swarthmore’s Government Web site attests that “noise levels in Swarthmore are projected to increase between 350 percent and 925 percent.” In reality, it is the decibel values that will increase at that rate, not the actual effective noise level.

   “I do think before publishing a map that has such a large effect, it’s important to check with a professional,” Everbach said. At a meeting within the past month, Everbach and Swarthmore Council Chairman Reilly both voiced their doubts about the ambiguity of the maps that represented the likely consequences of the FAA changes. Everbach said that his reason for questioning the way the information was presented was so that people could easily and accurately interpret the data. “I wanted to make sure that people addressed the magnitude of the problem,” he said. “It’s not quite as bad. I do personally think we should still fight this, but for the right reasons.”

   In 2004, the FAA began to promote an alteration in air traffic patterns in order to decrease problematic flight delays. In addition to changing plane routes, the FAA proposed that an extension of Philadelphia International Airport’s current runway 17-35 would further ensure that delays would be dramatically less in the future. Although the issue received very little attention at the time, politicians and citizens alike have since voiced their opposition to the implementation of these plans. Currently, the county is focusing on developing a map of the projected alterations in noise measured in sones. Everbach said that he believed that this misrepresentation of information was merely a result of unawareness. “There will be some embarrassment,” he said. “I would like to believe that it’s a product of ignorance all around.”

   Everbach did say, however, that some people’s misapprehension of the situation might have allowed the issue to be blown even more out of proportion. “Based on their incorrect understanding, some politicians such as Tom Gannon and, to an extent, Curt Weldon have circulated [this information] at taxpayers’ expense,” he said. County Manager of Transportation Planning Tom Shaffer said that as soon as the information on how the county will be affected in terms of sones is complete, it will be made available. “We’re making an effort to make the information very accessible to municipal governments and the public,” he said. “We’ve taken advice from Mr. Everbach, and we’re planning on changing the map to reflect these modifications.” County Executive Director Marianne Grace said that the slight modifications in the information should make it so that it will be much more representative of what people will experience on a day-to-day basis. “We wanted to make this tangible — will it be as loud as the pounding of a hammer?” she said. Grace said that the fact that the distinction between decibels and sones will be made apparent in future maps will make little difference to her. “To me, it doesn’t have a great impact,” she said. “I still think the changes will have a significant effect.”

Source - The Phoenix