Field evaluations of hearing protection devices at surface mining environments
A study was conducted to evaluate the effectiveness of circumaural hearing protection devices and their predictability when they were being worn by mine employees performing normal work duties. The method employed relied on a physical measurement of the noise reduction of the hearing protectors by utilizing two FM-wireless transmitting and receiving systems. One system measured the outside hearing protector noise level, the second system measured the inside hearing protector noise level. The noise level data of both systems was transmitted back to the corresponding receivers and was recorded onto a two-channel tape recorder. Three methods of evaluating hearing protector performance were explored and compared to the Environmental Protection Agency, Noise Reduction Rating (EPA NRR) values. They were, (1) predicted National Institute for occupational Safety and Health`s (NIOSH) method No. 1 values, (2) field-calculated NIOSH No. 1 values, and (3) measured dBA reduction values, which was the arithmetic A-weighted differences between both microphone locations. The majority of the data was obtained on operators of mobile strip equipment, such as bulldozers, front-end-loaders, and overburden drills. A total of 107 individual tests were conducted using 11 different hearing protectors. The results indicate that the amount of protection, which can vary significantly, is related either to the spectrum shape of the noise, or the C-weighted minus the A-weighted (C-A) value. This is consistent with other researchers. The field measured noise reductions were equivalent to the EPA NRR values when the C-A values were negative or approaching zero. When the C-A values increased, the measured noise reductions significantly decreased.
- Research Organization:
- Mine Safety and Health Administration, Denver, CO (United States)
- Sponsoring Organization:
- Department of Labor, Washington, DC (United States)
- OSTI ID:
- 10147356
- Report Number(s):
- MSHA/IR-1213; ON: DE94011052
- Resource Relation:
- Other Information: PBD: 1993
- Country of Publication:
- United States
- Language:
- English
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