The blasting underground cause’s high frequency subaudible noise measured in terms of air over pressure. The results (Table 13.2) covering wholly manual, partly mechanised with cola cutting machines and partly mechanised with SDL loading, showed reduction in the noise level underground. The mechanised mines have lower noise problem in comparison to the old conventional mines operating with haulage and coal cutting machines. The result of a noise survey for a coal mine conducted by Director General Mines and Safety (DGMS) is summarised in Table 13.1, which indicates noise over 90 dB by the drills, breaking and crushing units and transport system underground. The transfer points of the coal underground were the main point of the noise menace. ![]() The values increased in many Indian mines because of poor maintenance of the machines and exceeded the permissible limit of 90 dBA for 8 hours per day exposure. In a mine of Singareni Collieries Company Ltd.,-Bihar, the noise level near fan house, conveyor system shearer and road headers was reported to be within 92-93 dBA. The ambient noise level due to different operations in underground mines varies within 80-104 dBA. The most noise generating equipment underground are the haulage, ventilators-main, auxiliary and forcing fans, conveyor transfer points, cutting and drilling machines.
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