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which the human ear is most sensitive. Representative outdoor and indoor noise levels in units of <br /> dBA are shown in Table 2. <br /> TABLE 2 Typical Noise Levels in the Environment <br /> • <br /> Common Outdoor Activities Noise Level (dBA) Common Indoor Activities <br /> 110 dBA Rock band <br /> Jet fly-over at 1,000 feet <br /> 100 dBA <br /> Gas lawn mower at 3 feet <br /> 90 dBA <br /> Diesel truck at 50 feet at 50 mph Food blender at 3 feet <br /> 80 dBA Garbage disposal at 3 feet <br /> Noisy urban area, daytime <br /> Gas lawn mower, 100 feet 70 dBA Vacuum cleaner at 10 feet <br /> Commercial area Normal speech at 3 feet <br /> Heavy traffic at 300 feet 60 dBA <br /> Large business office <br /> Quiet urban daytime 50 dBA Dishwasher in next room <br /> Quiet urban nighttime 40 dBA Theater,large conference room <br /> Quiet suburban nighttime <br /> 30 dBA Library <br /> Quiet rural nighttime Bedroom at night, concert hall <br /> 20 dBA <br /> Broadcast/recording studio <br /> 10dBA <br /> 0 dBA <br /> Source: Technical Noise Supplement(TeNS),Caltrans,November 2009. <br /> Because sound levels can vary markedly over a short period of time, a method for describing <br /> either the average character of the sound or the statistical behavior of the variations must be <br /> utilized. Most commonly, environmental sounds are described in terms of an average level that <br /> has the same acoustical energy as the summation of all the time-varying events. This energy- <br /> equivalent sound/noise descriptor is called Leq. The most common averaging period is hourly, <br /> but Leq can describe any series of noise events of arbitrary duration. <br /> Page 5 <br />