Noise variability in underground room and pillar coal mines.

Noise in an underground coal mine has dominant components generated mainly from 3 sources: (a) continuous mining machines, (b) roof bolters, and (c) cars/vehicles used to transport personnel and/or coal. Each of these 3 noise sources also has a number of well-defined sub-sources with their own noise characteristics. Sound level meters were used to collect noise data in the form of instantaneous readings and also to check calibration of other sound measuring instruments. The most useful information was obtained from a spectrum analysis of continuous digital recordings of noise over time. This paper discusses the variability or dynamics of generated noise in both frequency and time domains in relation to several independent variables related to coal extraction and transportation processes.