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Chapter 3. Fundamentals of Traffic Noise <br />............................ <br />traffic noise reports are typically reported in terms of dBA. Table 3.1 shows typical <br />A -weighted noise levels. <br />Table 3.1. Typical Noise Levels <br />Common Outdoor Activities <br />Noise Level <br />Common Indoor Activities <br />— 110 — <br />Rock band <br />Jet flyover at 1,000 ft <br />—100— <br />Gas lawnmower at 3 ft <br />—90— <br />Diesel truck at 50 ft at 50 mph <br />Food blender at 3 ft <br />— 80 — <br />Garbage disposal at 3 ft <br />Noisy urban area, daytime <br />Gas lawnmower, 100 ft <br />— 70 — <br />Vacuum cleaner at 10 ft <br />Commercial area <br />Normal speech at 3 ft <br />Heavy traffic at 300 ft <br />— 60 — <br />Lar a business office <br />Quiet urban daytime <br />—50— <br />Dishwasher in next room <br />Quiet urban nighttime <br />— 40 — <br />Theater, large conference room (background) <br />Quiet suburban nighttime <br />— 30 — <br />Library <br />Quiet rural nighttime <br />Bedroom at night, concert hall (background) <br />—20— <br />Broadcast/recordin studio <br />—10— <br />Lowest threshold of human hearing <br />— 0 — <br />Lowest threshold of human hearing <br />Source: California Department of Transportation, Technical Noise Supplement, Table 2-5 (September 2013). <br />dBA = A -weighted decibel(s) <br />ft = foot/feet <br />mph = miles per hour <br />3.6. Human Response to Changes in Noise Levels <br />As discussed previously, doubling sound energy results in a 3 dB increase in sound. <br />However, given a sound level change measured with precise instrumentation, the <br />subjective human perception of a doubling of loudness will usually be different than <br />what is measured. <br />Under controlled conditions in an acoustical laboratory, the trained, healthy human <br />ear is able to discern 1 dB changes in sound levels when exposed to steady, single - <br />frequency ("pure -tone") signals in the midfrequency range (1,000-8,000 Hz). <br />In typical noisy environments, 1-2 dB changes in noise are generally not perceptible. <br />However, it is widely accepted that people are able to begin to detect sound level <br />increases of 3 dB in typical noisy environments. Further, a 5 dB increase is generally <br />perceived as a distinctly noticeable increase, and a 10 dB increase is generally <br />perceived as a doubling of loudness. Therefore, a doubling of sound energy <br />Fairview Street Improvements from 9th Street to 16th Street 13 <br />and Bridge Replacement Project Noise Study Report <br />