Comparison of noise reduction values for fit tests and work in coal mines

Abstract

At present exposure limits, one in four workers will develop a permanent hearing loss as a result of mining coal (Prince 1997). Mine Safety and Health Administration (MSHA) inspectors found in the period of 1986-1992 that approximately 25% of coal miners' daily noise doses exceeded MSHA's PEL. Virtually all mines have hearing conservation programs and virtually all miners are issued and told to wear either ear muffs or ear plugs. Nevertheless, miners still have a high rate of noise induced hearing loss (NIHL). An important question is to what degree the ineffectiveness of hearing conservation programs is due to failure of miners to wear muffs and plugs properly when they are needed and how much is due to inadequacies of hearing protectors. If the former is important, can technological innovations provide means to improve use of muffs and plugs. If the latter is important, can individual fit-testing improve noise reduction (NR) values achieved by miners. A related issue is whether fit-testing in an office environment adequately predicts NR values achieved during work if non-wearing times are excluded. To address those issues, WVU is conducting studies in a lab and in coal mines that primarily involve measuring sound levels in the ear (SPLear) concurrently with sound levels at the shoulder (SPLsh), allowing computation of NR values for protectors.