The modification of a percussion drill, of the type used in mining, to reduce the noise to permissible levels requires drastic reduction of exhaust noise, drill-steel resonance noise, and machine noise from the drill mechanism. Efficiency and utility of the portable tool must be retained in the quiet version. The impact of the piston on the drill steel generates excessive airborne and structure- borne noise, and containment and suppression of this noise at or near its source is vital. A rotation chuck machined from manganese- copper damping alloy, when substituted for the standard steel chuck, enclosing the impact area within the drill, very effectively suppressed the shock noise from the impacting surfaces. Test-stand data show that greater noise reduction was achieved by this method than was obtained by some external covers when the steel chuck was in use. Technical problems and implications of using these alloys are discussed.
J. Acoustical Soc. America, V. 54, No. 1, July 1973, PP. 278