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Acoustics 08 Paris 1967The use of the DNL metric in airport noise zoning is based in the works of Schultz, that were later improved by Fidell. The basic idea is to use the percentage of highly annoyed people as a parameter to organize the area around airports. In urban zoning it is recommended to use the equivalent sound level LAEQ, which uses different criteria to day and night periods to define the land use. With regards to airport noise one may use LAD and LAN metrics which are the equivalent sound levels determined for day and night period, respectively. In this case, the maximum levels chosen to the establishment of the zoning are based on the land use. It is possible, through a simple equation, to determine the DNL level associated to a LAD, LAN pair. The inverse problem, however, has not a unique solution, once this relation depends on the number of daily and night flights of the airport. Thus, the use of DNL in airport noise zoning may lead to completely different results for different airports. Examples are presented and discussed for two main brazilian airports: Recife and Congonhas.

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This study compares metrics for environmental noise diagnosis in schools at airport vicinity. The goal is to analyze and identify the most suitable criteria for scaling aircraft noise impact over schools, during landing and take-off operations. A Brazilian case study is conducted, based on the noise mapping and sound level verification. The day-night average noise level (DNL) and the time above limit (TA) are investigated using acoustic simulation and noise mapping and in order to identify the critical receivers. Results of DNL and TA for two schools at airport surroundings show that the criteria adopted by the municipal and airport authorities to describe the airport noise are unsatisfactory and do not reflect the intermittent behavior of this type of noise. It was verified that individual receiver analysis, based on noise interruptions thought TA parameter is more suitable for evaluation of noise impact over schools at airport vicinity.