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NIOSH - National Institute for Occupational Safety and Health
NIOSH Hearing Loss Research Program Review NIOSH Publications on Noise and Hearing The National Academies - Advisors to the Nation on Science, Engineering, and Medicine

What will the program achieve?

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Research Goal 1

Research Goal 2

Research Goal 3

Research Goal 4

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What will the program achieve?
Research Goal 3.2 - Reduce noise generated by roof bolting machines using wet and mist drilling

The following related research and development efforts are currently being conducted by the HLR program. Outputs, transfers, and outcomes are expected in the near future.

Health Hazard Study of Mining and Construction Surface Drilling OperationsThis research project is intended to develop engineering noise controls for air rotary surface drill rigs used in the mining and construction industries. Field investigations on air rotary drill rig operators have shown that the operators are being overexposed to noise. In addition, results from over 300 audiogram tests show that drill rig operators have a hearing loss. Air rotary drill rigs are used by the mining and construction industries to drill vertical holes into the earth for such purposes as establishing water wells, environmental monitoring wells, gathering of geo-technical information, engineering designs, and drilling blast holes during mining and construction projects.

Two engineering noise controls are currently being developed to help protect operators on cab and non-cab air rotary rigs. One of the noise controls utilizes a commercially available hydraulic muffler to reduce structural noise vibration of the control panel in cab mounted rigs. Tests results on a rig with hydraulic mufflers installed by HLR researchers showed a 5 dB(A) noise reduction during rig idle and a 4 dB(A) reduction during hammer drilling. The other noise control device is referred to as the “partial cab.” The partial cab is a prototype design to protect operators from noise levels on drill rigs without cabs. Test results showed an 8 dB(A) reduction in noise levels during hammer drilling. Both of these controls reduce drill rig noise levels which have the potential to reduce the average noise exposure that operators experience during an eight hour shift. Knowledge gained from this project will be communicated to the construction and mining industries and research institutions through partnership councils, research journals, industry-centered publications, seminars, and conferences. The effects of the engineering controls are expected to begin in 2006, when test results are finalized and published.

Partial Cab









Partial Cab: Protects the drill rig operator from over exposure to noise

Reducing noise on Roof Bolting Machines
The HLR program is working with the Noise Partnership Committee to evaluate and develop various controls for reducing noise related to roof bolting machines. The goal of this research is to determine the major contributors to an operator's noise exposure during the drilling and bolting cycle and then reduce the noise generated during these cycles by 10 dB(A). The investigation will provide methods and solutions for minimizing overexposure to noise among operators of roof bolting machines. Research on engineering noise controls for roof bolting machines will be completed in 2007. To raise industry awareness of these controls, results will be disseminated through publications in journals and trade magazines and presentations at industry briefings related to noise exposure in the mining industry. By reducing roof bolting machine noise by 10 dB(A), we anticipate that 90% of roof bolting machine operators’ exposure to noise will fall below MSHA's permissible exposure limit by 2008.

Roof Bolting Machine









Roof bolting machine testing in acoustic test chamber at PRL

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