| Summary: | The aim of the investigation is to identify and interrelate particular parameters that influence the magnitude of noise levels to which rock drillers are subjected. The percussive rock drill is known to be an excessively noisy machine. Currently, exhaust mufflers and other silencing devices are being developed but as yet acceptable noise levels have not been established. The definition of acceptable sound power levels for drills must recognize that the sound levels to which the drill operator is exposed are modified by the acoustic properties of the working environment.
For the initial phase of the investigation a representative rock drill was selected as a noise source. Comparative sound levels generated by this machine were measured in a free field environment and in typical underground working places. Increases in the sound pressure levels in each octave band from 63 to 16,000 hertz were observed when the drill was operated in both stopes and drifts.
For the subsequent phase of the investigation, studies were conducted on an assortment of commercially available rock drills. The changes in measured sound levels have been related to:
the acoustic properties of the working place,
the drill position relative to the walls,
the length of drill steel exposed from the hole, and
the drill air supply pressure.
Based on the measurements taken throughout the investigation, sound pressure level correction factors are proposed. By applying these factors to sound levels generated under free field conditions, predictions of rock drill sound pressure levels present in underground working places can be made. In addition, when studies of rock drill noise levels in various operating configurations are being conducted, use of the factors permits reduction of observed sound level measurements to a common datum. === Applied Science, Faculty of === Mining Engineering, Keevil Institute of === Graduate
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