Page 254 - Advances In Productive, Safe, and Responsible Coal Mining

Engineered noise controls for miner safety and environmental responsibility 233

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Fig. 12.15 Sound pressure level radiated by standard and damped drill steels with 1 / 8 -in.
(4.1-cm) drill bits.

Sound power levels radiated by a standard drill steel when drilling into granite were
compared to the sound power radiated using the CDSE under the same conditions. In
addition, tests were conducted with varying gaps between the top of the CDSE and the
bottom of the drill media. Varying gaps would determine how tight of a seal was
needed between the CDSE and the rock media in reducing sound power levels.
Gap lengths of 15.24cm, 10.16cm, 7.62cm, 5.08cm, and no gap were tested.

(B)

(A) (C)

Fig. 12.16 Prototype of the collapsible drill steel enclosure (CDSE) noise control concept:
(A) installed on a roof bolter machine, (B) outer layer, and (C) inner spring.