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[~ <br />Site C-4 <br />~ • l <br /> Measurement data showed a noticeab <br />e decrease in A-weighted <br /> sound levels of 5 dBA from last September's measurements when <br />C a value of 71 dBA was recorded. <br /> Site C-6 <br /> No significant changes were observed. <br /> Site L-8 <br /> Other than a 6 d6 drop at 63 Hz the shape of the octave band <br />~; <br />L; signature for this site remained essentially unchanged from <br /> September, 1979. The total acoustical energy as reflected by <br />~' <br /> the A-weighted measurement decreased 4 dBA since last <br /> September to 72 dBA. <br /> Site C-10 <br />• The octave band analyses revealed little change from the data <br /> recorded last September, however there was consistent drop <br />C over all frequencies which yielded a drop of 6 dB in <br />-' <br />~ A-weighted values. This may possibly be due to the inac- <br />.: <br />tivity of belt 5. <br />1 <br /> d) Truck Dump - Sites TD-I, 2, 3 <br /> <br /> Sound level measurements within the truck dump area revealed <br />-~ that significant changes have occurred in the acoustic environment <br /> since last September. Our observations were that the truck dump <br />r <br /> baghouse fan and stack have become the dominant noise sources <br /> within the lower mine facility area. in particular, mid and high <br />,_ frequency sound levels have increased. This coupled with visual <br />. • inspection indicates wear-induced Heise increases from vibration <br /> and loose or worn mounting hardware and sheet metal in the <br /> fan/stack complex. Measurement results at individual sites were: <br />