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_~ b _.'naorparBCed 1313 5th street s.e. · suite322 · minneapolis.mn55414 telephone: 812-331-4571 · fax: 812-331-4572 2 February 1994 Michael Falk city of Roseville 2660 Civic Center Drive Roseville, MN 55113 RE: Advance Circuits - Noise Measurements at Anderson Residence Dear Mike: We were able to take advantage of the January thaw to make noise measurements at the Anderson residence. We began monitoring as soon as the temperature began moderating, but unfortunately the first night was lost due to the cold. However, we were able to obtain readings for three consecutive nights when both the temperature and wind permitted the collection of reliable data. These dates were (Saturday (Jan 22-23), Sunday (Jan 23-24) and Monday (Jan 24- 25). Three nights were monitored since the the first night and then the second night showed readings substantially below the readings taken last June. Sound propagation in the winter with snow cover is similar to sound propaga- tion in summer with grass and leaves. Actually, the attenuation under winter conditions may be less. Snow on the roof provides more absorption of sound than the hard roof, although the distance between the source and the edge of the roof is small. Therefore, this effect is likely to be less than 1 dBA. The readings were taken without the knowledge of Advance Circuits. However, we also had no knowledge of what equipment was operating at the time. The readings taken during this time period are comparable to those taken in June only if all equipment that might be used throughout the year was in operation. Dan Mccarthy of Advance Circuits was contacted on 1 February 1994 to check on equipment operation during the monitoring periods. He indicated that all equipment was operating normally during that period. The results of the noise readings are summarized on the attached graphs. These measurements demonstrate a significant reduction in noise level (9 dBA in the quietest period) from the readings taken in June 1993. They also indi- cate that the L50 sound levels remained below the 50 dBA standard except for small (1 dBA) excedance between 6-7 am on Tuesday morning. This could easily be due to traffic noise in the area which generally increases during this time period.