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<br />Kim Lee regarding Noise Levels at Wilcoxon Residence <br />2 January 1998 <br />Page 2 <br /> <br />In addition to overall dBA noise measurements, sound spectrum measurements were also <br />made around noon on 23 October 1997. The objective of these measurements was to <br />identify the strong tonal component of noise which is considered to be especially <br />objectionable by Ms. Wilcoxon. Sound level "shapshots" were taken between 12:35 and <br />1 :03 pm and are shown in EXHIBIT 3 through EXIllBIT 6. <br /> <br />The tonal component, centered at 315 Hz, is approximately 10 dBA above the remainder <br />of the sound spectrum at this frequency. A level of 10 dBA can be considered to be an <br />intrusive level and because of its tonal content (Le. a steady and clearly identified tone), <br />this noise could be considered to be especially intrusive relative to the overall noise level. <br />This sound appears to be associated with a cyclone fan and could probably be easily <br />identified when in closer proximity to the equipment. A reduction of this particular <br />sound level would probably provide a substantial benefit to the overall noise level. <br /> <br />In conclusion, the results of the 1997 noise measurements and comparison with the 1996 <br />measurements suggest that the fence as constructed provides some reduction in noise <br />level (4 dBA) although the level remains 3 or 4 dBA above the MPCA nighttime noise <br />standard. Measurement of spectral noise suggests that additional reduction of the sound <br />source with a strong tonal component around 315 Hz will provide a substantial addition <br />reduction in the perceived noise level at the Wilcoxon residence. <br /> <br />As before, I would be happy to work with ACI and the City to make any further <br />recommendations for treatment of sources or placement of barriers. More detailed data <br />from my measurements in October 1997 can be made available if that would be helpful. <br />Thank you for the opportunity to assist the City on this issue. <br /> <br />cc: Lisa Wilcoxon <br /> <br />roseOl02.mem 97083 <br /> <br />~ <br />