The noise and vibration levels of four jumbo drills were characterized and a survey of percussive rock drill usage is reported. A Gardner-Denver DH 123 drill was chosen as a demonstration drill, and extensive noise diagnostic studies were performed. Noise control treatments were designed, developed, and evaluated in a reverberant drill test facility. The treatments consisted of an integral enclosure-muffler for the drifter, vibration isolation of the drifter from the enclosure and feed, and a drill steel sheath. A 19-dba reduction in overall sound power level was achieved with no loss in drilling rate. The prototype retrofit treatments were field tested in an aboveground mine and in a production section of an underground zinc mine. Long-term durability and operator acceptance of the enclosure-muffler treatment were excellent. Preliminary evaluation of the drill steel sheath was encouraging, although additional testing is required.