PURPOSE:  The objective of this project is to determine and implement appropriate engineering controls to reduce excessive exposure to noise on the job and prevent additional cases of Noise Induced Hearing Loss (NIHL) related to roof bolting machine operators.

RESEARCH SUMMARY:  Noise is one of the most pervasive health hazards in mining. The National Institute for Occupational Safety and Health has identified occupational NIHL as one of the ten leading work-related diseases and injuries. MSHA coal noise samples from 2000 to 2002 show that 65% of the equipment whose operators’ noise dosage exceeded 100% is comprised of seven different types of machines: auger miners, bulldozers, continuous miners, front end loaders, roof bolting machines, shuttle cars (electric), and trucks. Of these, the roof bolting machine was the third most common type of equipment whose operators exceeded 100% dosage.

The relationship of noise generated by the drilling and bolting cycles of a roof bolting machine utilized in underground coal mining and the attributed noise exposure of the operator will be investigated. A noise survey of roof bolting machine operators will be conducted to identify the tasks which are significant contributors to the operator’s noise exposure. This will be accomplished by placing a dosimeter on the operator to record his noise exposure while simultaneously conducting a time-motion or task observation. The drilling and bolting duty cycles will be extracted from the data to determine how much noise exposure to the operator is generated by these individual tasks. Sound power measurements will then be conducted on the roof bolting machine in the PRL reverberation chamber, along with above ground measurements in a free-field noise environment. Additionally, underground measurements will be performed using a sound level meter to record the sound levels of the roof bolting machine thru several duty cycles. The data will be analyzed to assess the relationship of the drilling and bolting cycles to the noise exposure associated to the operator. Noise sources will be identified and ranked according to their percentage of contribution to the overall sound level generated by the drilling and bolting cycles.

From this, NIOSH will develop and test conceptual engineering controls designed to reduce the noise emission of roof bolting machines and thus, reduce the noise dosage exposure and NIHL of their operators. This information will be disseminated to the mining industry for their use in retrofitting existing equipment and as an aid for a quiet-by-design approach for developing the next generation of equipment.