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FL Environmental Noise Monitor - A measuring device for determining the levels of noise in the environment. An environmental noise monitor will have a variety of readouts the operator can select and a recording capability so that data may be collect- ed for extended periods of time. Equivalent Sound Level (Leq or LEQ) - The average level of sound for a period of time. This measure is expressed in decibels and reflects the average level in either one of the weighted measures (dBa, dBc) or linear (just plain old dB) . Exceedance Threshold - The term for a setting in an environmental noise monitor that will cause the monitor to record the level and time of noise. The monitor will record the time the noise exceeds the threshold and (usually) the level of the noise. F. "Fast" response - A setting on a sound level meter or environmental noise monitor that indicates the instrument is showing the results of readings that last for about one-eighth of a second each. ' Hourly Average Noise level (HNL) , Hourly Noise Level -- The Leq for a period of one hour beginning on the Hour. This is the base figure for calculation of the Ldn or CNEL. Integrated Sound Level - Mathematical addition of sound for a period of time. Since the scale for sound measurement is logarithmic, the numbers achieved do not look as though they reflect the total energy of the sound. one of the better {` comparisons is to electricity, just as watts and kilowatts show an amount of electrical energy, so decibels of integrated sound level show the amount of energy of sound. The person dealing in sound differs from the straight line mathematician because for him, two and two really do equal five. Interval - A setting used by an environmental noise monitor to a determine the time period for an average noise level. There may be several standard intervals used by the monitor as well as a specified period. Levels Exceeded (LXX) - The noise levels exceeded for a specified period of time. The reference to a level exceeded would be as 1IL50 equals 55 dBa" meaning that the level of 55 dBa is exceeded for 50% or one half the time. L90 would mean that level exceeded for 90% of the time and would be a lower level than L50 and L5 would be a higher noise level (exceeded only 5% of the time) . Maximum Noise Level (MNL, Lmax) - The loudest level of noise reached as indicated on a sound level meter or environmental noise monitor in either "fast response" or "slow response" . 9 F_ i f