The mining industry still faces some serious challenges in developing the noise control technology needed to provide a quieter work place. One of the most difficult systems to control is the percussion rock drill. There are instances in which rotary drilling is applicable, but this U.S. Bureau of Mines paper concerns operations in rock types that require percussion drilling. The high stresses required for effective hard rock drilling preclude rotary drilling as an alternative, minimizing the prospect of a quiet drilling mechanism. There has been a significant research effort devoted to refining rock drill performance in terms of efficiency and reliability. Fortunately, the information available is often useful in terms of controlling the noise of the drill as well. The major noise sources break down into three broad divisions: air exhaust (pneumatically powered drills), drill body radiated noise (pneumatically and hydraulically powered drills), and drill steel noise. The noise source of interest in this paper is the drill steel, which is a significant contributor to the overall sound levels produced by percussive rock drills, in some instances controlling the lowest possible noise level available from a quieted design.
Paper in Noise-con 90. Univ. Texas, Austin, 1990, PP. 403-408