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AfNoisefModelingfA _.___.___f <br /> 9.A. - Page 109 <br /> Exhibitv4-2 n.6oundhExposureg_eveluConcepty <br /> A <br /> U) <br /> a Sound Exposure <br /> C.) Level SEL <br /> Q� _ <br /> lO <br /> a) Maximum A-level - <br /> a) <br /> J <br /> N <br /> � SEL= <br /> Time integration of <br /> A-weighted noise <br /> level divided by <br /> reference duration <br /> t <br /> Duration of Event <br /> Q (several seconds) Reference Duration <br /> (1 sec.) <br /> Time f <br /> Source f Brown-BuntinfAssociates f I nc.f Novembers 2004 f <br /> Preparedf by f ESAf Airports,fAugustf2013. <br /> Communityd AioisecEquivalenthLevek(CNEL): The cumulative noise descriptor required for <br /> aircraft noise analyses in the State of California is the CNEL. CNEL is used to describe <br /> cumulative noise exposure for an annual-average day of aircraft operations. The CNEL is <br /> calculated by mathematically combining the number of single events that occur during a 24-hour <br /> day with how loud the events were and what time of day they occurred. <br /> CNEL includes penalties applied to noise events occurring after 7:00 p.m. and before 7:00 a.m., <br /> when noise is considered more intrusive. The penalized time period is further subdivided into <br /> evening(7:00 p.m. through 9:59 p.m.)and nighttime(10:00 p.m. to 6:59 a.m.). CNEL treats <br /> every evening operation as though it were three and every night as though it were ten. This <br /> "weighting"adds a 4.77 dB penalty during the evening hours and a 10 dB penalty during the <br /> nighttime hours. <br /> Because of the interrelationship between the weighted number of daily noise events and the noise <br /> levels generated by the events, it is possible to have the same CNEL value for an area exposed to <br /> a few loud events as for an area exposed to many quieter events. <br /> The CNEL metric used for this aircraft noise analysis is based on an average annual day of <br /> aircraft operations, generally derived from data for a calendar year. An annual-average day <br /> SanfCarlosfAirportV A-5 ESAfAirportsf/130753f <br /> ALUCPf W hitef Pape/ Junef2014f <br />