Reducing longwall noise with acoustical material on the shields - A preliminary analysis

Along with increased production from longwall units has come the likelihood of increased worker noise exposures. In recent years, equipment has become larger, more powerful, and noisier than its predecessors. For these reasons, the U.S. Bureau of Mines [USBM] is investigating worker noise exposure on longwall faces and researching possible solutions to reduce this exposure. Part of this research effort involves studying the effect of covering the underside of longwall shields with acoustical material to reduce reverberating noise along the face. Experiments using acoustical absorptive insulation were conducted at the full scale simulated longwall test facility located at the Pittsburgh Research Center. Longwall noise measurements recorded underground were simulated in the test gallery. The undersides of ten 1.5 m [5 ft] wide shields were covered with acoustical material. Tests were run in which 1.2 m [4 ft], and 2.4 m [8 ft] wide sections of acoustical material were used to cover the undersides of the shields, shearer body, and the shield supports. Sound levels were recorded every 1.5 m along a 15.2 m [50 ft] section of the simulated face for all of the conditions tested, including the baseline condition with shields having no acoustical material. The analysis of themore » data indicated that a 2.0-3.0 dBA noise reduction was achieved between the shearer drums and a 4.0-5.5 dBA attenuation was attained upwind of the headgate drum Sound pressure level reductions in this range are equivalent to eliminating approximately 40 - 60% of the acoustic energy.« less