Investigations of personal noise dosemeters for use in coalmines

Sound level meters are suitable for measuring the noise emission of mine machinery, but they are not convenient for measuring the full-shift noise exposure of underground workers, as difficulties are encountered in siting the instrument close to the workman and the varying noise levels necessitate frequent readings throughout the shift. The use of personal noise dosemeters has therefore been examined; the choice of model was limited by intrinsic safety requirements.

Laboratory tests of two models of dosemeters indicated that they generally complied with the requirements for industrial grade sound level meters. Underground trials were carried out to compare measurements of mineworkers’ exposures made with (a) sound level meters carried by an investigator, (b) dosemeters worn by the investigator and (c) dosemeters worn by workmen. The statistical reproducibilities of measurements for the same man on different days and between different men carrying out nominally similar duties were examined.

Considerable differences, > 6 db(A), between measurements by sound level meter and dosemeter were observed, the dosemeters giving the higher values, of ca . 2.5 db(A) on average. The dosemeters were considered to give the better estimates. Statistical analysis indicated that the mean of five dosemeter results lay, to 95% confidence, within ± 3 dB of the true mean. Some instrumental defects were identified.