Agenda - 06-27-1983 - Laserfiche WebLink

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1 Although these refinements make EPNLs difficult Ito calculate without computer analysis of the noise , the refinements emerged from laboratoryexperiments in which people were asked to judgeithe loudness of aircraft events . Many people feel that annoyance caused by flyovers increases during these hours because background noises are lower at night ; thus making aircraft noise more intrusive . Therefore , to account forithe supposed increased annoyance to events occurring at night , NEF adds a weighting of approximately 12 dB to each EPNL value obtained for operations between the hours of 10: 00 p .m. and 7:00 a .m. The exact value of the weighting s engineering g an en g eating judgement , not one for which there are conclusive community response data . The NEF value at any point , then , is the energy P , , gy average of the EPNLs ( including the weighting for night flights) for each aircraft operation during a 24-hour period . A constant is subtracited from the total so that the resulting NEF value will be significantly different from the EPNL value a help in avoiding confusion between the two measures . NEF o EPNL + 10 log10 (Nd + 16. 67 N n) -88 . lir : For each of the cumulative pressures , the exposure at a point is considered to be the result of the average level adjusted for any nighttime weighting. "Average" here is an energy average , which recognizes that noisy events produce a greater impact than quiet events . The result is similar to what we found in decibel addition . equivalent Sound Level (Leq) Leq is the steady A-weighted sound level over any specified period (not necessarily 24 hours) that has the same acoustic energy as the S 19 .. •p>,:'1't'0'.•.w.l lPd^."#Yl..,'.°•i�'P'��.�-,�TI'k-�'a�.._ _..�•._._.,_ L::a ..._''I{Imr:;o.....da••...a....,__._...... ......