Laboratory Noise Testing of a Jumbo Drill

There is a high prevalence of hazardous noise exposures among the nation's mining workforce, with 76% of miners overexposed to noise and 27% suffering from noise-induced hearing loss. Field time-motion and dosimeter studies have revealed that jumbo drill operators are frequently overexposed to noise and may be subjected to noise levels exceeding 100 dB(A). To address these problems, NIOSH initiated a research project seeking to develop noise controls to reduce the sound level at the jumbo drill operator's location and thus reduce the operator's noise exposure. Key to the success of this effort is determining the primary noise sources on a jumbo drill. Earlier project research included noise source identification testing using beamforming techniques in the field. This paper discusses similar beamforming testing conducted on a single-boom jumbo drill in an acoustical laboratory environment. This testing revealed primary noises along the drill string and also at the drifter. Additional testing documented the effect of drill bit diameter on the sound power emitted by the jumbo drill during drilling.