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<br />l.r, Dale Ream <br />Cooley Gravel Company <br />20 I.~arc}? 1975 <br />Fade 9 <br />Sound level .measurements were made on 18 and 20 February and <br />6 and 18 :•:arch 1?75 to evaluate +?oise level contributions <br />from i:orrison C:uarry on surrcundi+?; areas. Five recording <br />stations •sere set-u~ to z:?onitor noise levels wit;? and without <br />the quarry opera-tiny, 1leasurements v:ere made at the follo::in <br />sites (also see figure 2) <br />Site A cast Edge of Cooley Gravel Cor.,pany's procerty, <br />500 feet east of final crushex•. <br />Site B Site of residence nearest to the quarry, at <br />corner of Forest and Vine. <br />Site C Colorado State Highway Department maintenance <br />Station on state HiAh:vay 8. <br />Site D Along north-south boundry betv+een Cooley <br />propert;~ and Denver ;~ountain Perri: Site. <br />Site E Along western boundry of Denver L:ountain Park <br />Site . <br />:he instrumentation at all five sites consisted of a General <br />Radio Sound Level i.;eter model 1551-C and an Es~terlir.e An~~us <br />Chart Recorder model A 601C. Zt was found that by counlinF; <br />the chart recorder to the sound level r:~eter, the noise level <br />was attenuated by seven decibels. Ho:vever, this effect was <br />Laren into consideration in calibration curve preparation <br />for the system. The sound .level meter was set cn t!?e "A" <br />frequency :•+eighting scale, since this has been selected by <br />noise control agencies as the general standard for noise <br />evaluation. <br />One of the primary sources of noise was transien+,s such as; <br />wind and the passing of cars and trucla on Colorado Route 8. <br />These transients are deviations from the background noise <br />level and have no relationship to quarry operations, The <br />quarry retains a cor.star,t level of operation over a period <br />of hours and cor.sequentiy could not contribute to transients, <br />bu-t rather only to the background noise level. On the other <br />hand, the transients only last between a few seconds and a <br />few minutes, and their source can be clearly recognized <br />since the sites c•+ere continuously moni+.ored by an operator. <br />Auto+~:obile transients are characterized b5• a noise level <br />peak of 63 cib and a duration of up to ten seconds, while <br />