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APPENDIX A <br /> ACOUSTICAL TERMINOLOGY <br /> AMBIENT NOISE LEVEL: The composite of noise from all sources near and far. <br /> In this context, the ambient noise level constitutes <br /> the normal or existing level of environmental noise at <br /> a given location. <br /> CNEL: Community Noise Equivalent Level . The average <br /> equivalent sound level during a 24-hour day, obtained <br /> after addition of approximately five decibels to sound <br /> levels in the evening from 7:00 p.m. to 10:00 p.m. and <br /> — ten decibels to sound levels in the night before 7:00 <br /> a.m. and after 10:00 p.m. <br /> DECIBEL, dB: A unit for describing the amplitude of sound, equal to <br /> 20 times the logarithm to the base 10 of the ratio of <br /> the pressure of the sound measured to the reference <br /> pressure, which is 20 micropascals (20 micronewtons <br /> per square meter) . <br /> Ldn: Day-Night Average Sound Level . The average equivalent <br /> sound level during a 24-hour day, obtained after <br /> addition of ten decibels to sound levels in the night <br /> after 10:00 p.m. and before 7:00 a.m. <br /> Leq: Equivalent Sound Level . The sound level containing <br /> the same total energy as a time varying signal over a <br /> given sample period. Le is typically computed over <br /> 1, 8 and 24-hour sample p2riods. <br /> NOTE: CNEL and Lon represent daily levels of noise exposure averaged on <br /> an annual basis, while Le represents the average noise exposure <br /> for a shorter time period, gtypically one hour. <br /> Lmax: The maximum sound level recorded during a noise event. <br /> Ln: The sound level exceeded "n" percent of the time <br /> during a sample interval . L1p equals the level <br /> exceeded 10 percent of the time (190, L50, etc.) <br /> BBA <br />