While DNL might give airport planners and the FAA a convenient, uniform way of depicting average noise exposure for an average annual day using the average fleet mix, average ground tracks, average flight tracks, average aircraft performance characteristics, and average atmospheric conditions, it does not convey to residents how frequently they are or will be disturbed by noise. "There is growing evidence that the number and intensity of the individual noise events that make up DNL are more important to public understanding of the effects of noise around airports," according to senior staff at Wyle Laboratories.
"Further evidence of the disconect between DNL as a figure of merit and public acceptance is that airport officials and federal authorities are sometimes surprised by strong opposition to growth and expansion projects when they can project future DNL contours will be smaller than current contours because of a quieter future fleet mix. Frequency of operations is a component of noise exposure that defines the noise environment for many individuals (perhaps even better than average sound energy), and the sooner we incorporate frequency of operations into the analysis of airport noise exposure, the better we will manage public opposition to the many needed airport expansion projects."
Wyle's approach is to look inside DNL by calculating the number of minutes the maximum sound level exceeds specified thresholds in the average annual day (Time Above, or TA) and the number of times within the selected time period that noise levels exceed a specific threshold (Number of events Above, or NA). With detailed grid point analysis given locations in a study area, TA and NA can be calculated over a range of thresholds, so that residents can graphically see how airport operational changes will affect them.
"Several airports have now included some level of NA and TA analysis in their recent noise studies, and in each instance, the public response has been very positive, and airport official's concerns that providing this additional noise exposure information may lead to greater demands for mitigation have proven to be unfounded," said Wyle special projects director Bill Albee.
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Aircraft Noise Study for Barajas International Airport (Madrid, Spain)
EIS for Runway 27 at Boston Logan International Airport
Environmental Assessment for Ohio State University Airport/Don Scott Field
Joint Land Use Study - NAS Willow Grove (Pennsylvania)
Land Use Guidelines for New Rural Airports, Toronto, Canada
New Runway Environmental Impact Statement Dulles International Airport
Noise Study for Houston International Airport
Supplement to Louisville Airport FAR Part 150 Noise Compatibility Study
Alternative Analysis-Vancouver Intn'l Airport Master Plan
Boston Logan Airport Noise Study Massachusetts Port Authority
Nighttime Noise Analysis-LAX
Nighttime Noise Criteria-Land Use-HighPoint,NC
GTAA
GTAA1
Noise Analysis-Public Safety Facility-Washington Dulles Airport
Noise Analysis of Potential Day Care and School Sites
Noise Study - St. Petersburg
Noise Study - City of Eagan
Oakland Airport Decision
San Diego Airport Site Selection Program