The National Institute for Occupational Safety and Health (NIOSH) Pittsburgh Mining Research Division (PMRD) conducts a wide variety of mining-related health and safety research. As part of this research, PMRD’s Workplace Health Branch maintains a Noise Control Team tasked with developing noise controls to reduce future incidences of noise-induced hearing loss (NIHL) among the nation’s mining workforce. A noise control project that PMRD is currently investigating is the development of noise controls to reduce the noise emissions from jumbo drills. Operators of jumbo drills are frequently overexposed to noise, putting them at risk of NIHL. A key contributor to the noise at the operator location is the noise radiated from the jumbo drill string, or drill rod. Jumbo drilling is rotary-percussive in nature, and the drill string is mechanically excited by the cutting of the media as well as by a percussive hammer. These excitations travel from the bit/rock interface and from the drifter hammer into the drill string, vibrating the structure and causing it to radiate noise. The development of an instrumented drill string will allow NIOSH to quantify the forces within the drill string during drilling, providing critical information for the development of jumbo drill noise controls.

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