Mining Project: Engineering Noise Controls for Haul Trucks and Load Haul Dumps (LHDs)

Research Summary

Previous NIOSH survey results indicated that more than 90% of underground metal equipment operators were over-exposed to noise according to the MSHA permissible exposure level. Haul truck and LHD operators were particularly at risk, with typical noise doses exceeding 200% on average. Noise over-exposure can lead to noise-induced hearing loss (NIHL).

The purpose of this project was to develop, evaluate, and implement engineering controls to reduce noise over-exposures among haul truck and LHD operators. The project had five phases:

Phase 1. Early research focused on field studies to quantify noise dose accumulations and noise sources. Time-motion studies determined the causal relationship between job task and noise dose accumulation. NIOSH collected sound pressure and sound intensity measurements to determine which sources should be addressed initially. In addition, sound power level testing was conducted in the laboratory to evaluate the overall noise emission of the haul trucks and LHDs.

Phase 2. NIOSH developed a working relationship with equipment manufacturers to address the noise sources that are prominent contributors to operator noise doses. Noise controls expected to be original equipment or available for retrofit were developed through agreements with manufacturers. Less complicated noise controls were developed in-house by NIOSH.

Phase 3. This phase overlapped with Phase 2. As noise controls were developed, they were laboratory tested and those with promise were field tested. This sound pressure and sound power testing confirmed reduction in noise emissions. Field time-motion studies were conducted to quantify the expected reductions in noise exposures.

Phase 4. Licensing and distribution were finalized with a collaborating manufacturer. Noise controls developed in-house were documented and shared on the relevant NIOSH web pages, and MSHA was provided with the data.

Phase 5. Noise controls were formally evaluated to determine their effectiveness in reducing noise exposures and/or inducing behavioral changes in the work force.