A 1997 NIOSH analysis of a large number of miner audiograms, showed that by age 50, approximately 90% of coal miners and 49% of metal/non-metal miners had hearing impairment. In contrast, only 10% of the population that experienced non-occupational exposure to noise had any hearing loss by the age of 50 (Rider, 1999). Despite more than 30 years of regulation within the mining industry, 76% of miners are still exposed to hazardous levels of noise. This represents the highest prevalence rate of hazardous noise exposure in any work sector (Reinke, 2010).
Occupational hearing loss can be defined as hearing impairment of one or both ears, partial or complete, that results from a worker's employment job tasks. It includes both acoustic trauma and noise-induced hearing loss. Acoustic trauma is injury to the inner ear usually arising from a single or short-term exposure to intense noise (e.g., explosion). The damage is often related to a single incident. Noise-induced hearing loss, on the other hand, is cumulative damage to the inner ear over a period of months or years of exposure to hazardous noise (Fundamentals of Industrial Hygiene, 5th Ed, pp. 108).
Hearing loss is not the only hazard associated with noise in the mining industry. An additional problem with work environments exhibiting hazardous noise levels include impedance of audio cues of work processes and audio warning signals. This is especially crucial in mining where audio cues are imperative to safety.
Hazardous noise information is sub-divided into the following sections.