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A-2 <br /> ACOUSTICAL TERMINOLOGY <br /> NOISE EXPOSURE CONTOURS: Lines drawn about a noise source indicating constant <br /> levels of noise exposure. CNEL and Ldn contours are <br /> frequently utilized to describe community exposure to <br /> noise. <br /> SEL or SENEL: Sound Exposure Level or Single Event Noise Exposure <br /> Level . The level of noise accumulated during a single <br /> noise event, such as an aircraft overflight, with <br /> reference to a duration of one second . More <br /> specifically, it is the time-integrated A-weighted <br /> squared sound level for a stated time interval or <br /> event , based on a reference pressure of 20 <br /> micropascals and a reference duration of one second. <br /> SOUND LEVEL: The sound pressure level in decibels as measured on a <br /> sound level meter using the A-weighting filter <br /> network. The A-weighting filter de-emphasizes the <br /> very low and very high frequency components of the <br /> sound in a manner similar to the response of the human <br /> ear and gives good correlation with subjective <br /> reactions to noise. <br /> BBA <br />