Mining Topic: Hearing Loss Prevention Overview

What is the health and safety problem?

One out of every four mine workers has a hearing problem. Even worse, four out of five mine workers have a hearing impairment when they reach mid-60’s retirement age. Hazardous noise is the primary culprit—76% of mine workers are exposed to hazardous noise, the highest prevalence of all major industries.

What is the extent of the problem?

Noise-induced hearing loss (NIHL) is a permanent affliction that interferes with a mine worker’s ability to communicate with family, friends, and co-workers. It also creates a safety hazard when mine workers are unable to hear moving machinery and warnings. In addition, many afflicted with NIHL also experience tinnitus—a ringing or buzzing sound that persists in the absence of any real sound—which can be intensely stressful and annoying.

How is the NIOSH Mining program addressing this problem?

NIHL is being addressed in all areas of the mining industry, including both surface and underground for all commodities. Initially, the noise control efforts concentrated on underground coal mine noise and produced solutions for continuous mining machines, roof bolting machines, and the vibrating screens used in preparation plants. Current work by NIOSH Mining is addressing mobile equipment in underground metal/nonmetal mines, surface stone, sand and gravel mines, and underground coal mines.

The ultimate strategic goal of this research program is to reduce NIHL in the mining industry. To accomplish this goal, the program will:

1. Develop durable and practical noise controls for mining equipment.
2. Attain widespread industry implementation of noise controls.
3. Evaluate the short-term and long-term effectiveness of noise controls by acquiring surveillance data.

What are the significant findings?

A dual-sprocket continuous mining machine chain was developed that reduced sound levels by 2-3 dB(A) at the operator ear. It was commercialized by Joy Mining Machinery in 2008 and had been implemented on over 30% of the machines in the U.S. by 2012.

A drill bit isolator based on NIOSH Mining technology was found to reduce noise reaching the operator ear by 2-5 dB(A). It was commercialized by Corry Rubber and Kennametal in 2011.

A dual-sprocket urethane-coated continuous mining machine chain was developed and was found to reduce noise reaching the operator ear by 5-7 dB(A). It was commercialized by Joy Global in 2012.

A retrofit package was developed that reduced haul truck operator noise exposures by as much as 9 dBA and load-haul-dump operator noise exposures by as much as 2 dB(A). This solution was disseminated in 2014.

A new numerical modeling methodology was developed and implemented to predict acoustic radiation from a longwall system cutting drum. Based on the results of this method, various noise control options were explored, and a 3 dB(A) noise reduction was obtained with field test verification. Joy Global (Komatsu) and NIOSH obtained an international patent for this numerical modeling method in 2016.

What are the next steps?

The program is evaluating additional metal/nonmetal machines for noise hazards to be addressed through noise controls. NIOSH Mining researchers are also developing an enhanced modeling capability to develop noise controls more efficiently and conduct evaluations in the simulated acoustic environment of a computer-modeled mine. Work will continue to evaluate noise exposure and hearing conservation practices in stone, sand and gravel mines.

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