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WSB Engineering Carwash Noise Impact Assessment <br />David Braslau Associates, Inc. Page 5 <br />3.0 BACKGROUND SOUND LEVEL MONITORING <br /> <br />Background sound levels were taken on Friday afternoon, February 19, 2021 to capture typical <br />end of day traffic volumes. The monitored one-minute statistical sound levels are shown on <br />Figure 3.1. <br /> <br />The top curve labeled L(1) represents sound levels exceeded for 0.6 seconds of the minute or <br />essentially peak sound level of passing vehicles. The bottom curve labeled L(90) is the level <br />exceeded for 54 of the 60 seconds, and closely represents the minimum level occurring during <br />each minute. <br /> <br />The L(10) level hovers around 60 dBA. The state daytime noise standard is 65 dBA. The L(50) <br />level is well below the 60 dBA standard. <br /> <br />A more detailed short-term measurement of octave band sound levels was also taken during the <br />monitoring period. This shows some higher frequency levels as low as 30 dB, so there are <br />periodically some noticeably quiet times at this location without traffic present. <br /> <br /> <br /> <br /> <br /> <br />71