Investigation of persona1 noise dosimeters for use in coal mines

Sound level meters are not suitable for measuringthe noise exposure of underground workers over a full working shift. Difficulty is often encountered in siting the instrument close to the workman, and the varying noise level requires that readings be taken at frequent intervals throughout the shift. These difficulties do not arise when using personal noise dosimeters.The CEL 122 and Du Pont E-100 dosimeters are intrinsically safe for use in coalmines. A number of each type has been tested in the laboratory and field trials have been conducted at two collieries to assess their performance in mining conditions.No B. S. specification exists for personal noise dosimeters but the laboratory tests showed that the CEL 122 and Du Pont E-1OO mostly met the specification for industrial grade sound level meters. Results with the CEL 122 and Du Pont E-100 were in good agreement, and both models performed well in reproducibility tests. Measurements taken under controlled conditions near constant noise sources showed that Leq, dB(A) values derived from dosimeter readings differed little from values obtained with precision sound level meters. However, measurements with workmen underground sometimes showed large differences due to the difficulties noted above of using sound level meters. In such situations it is considered that the CEL 122 and Du Pont E-1OO dosimeter give a better assessment of the workman’s noise exposure, notwithstanding the fact that the instruments do not meet the specification for precision grade sound level meters.Trouble with the switches and spurious overload readings occurred often with the CEL 122 instruments, whilst three of the memory cells used with the Du Pont E-100 dosimeters developed faultsThe workmen did not find the dosimeters a hindrance, except during kneeling when they were liable to come off the trousers belt.