Page 262 - Advances In Productive, Safe, and Responsible Coal Mining

Engineered noise controls for miner safety and environmental responsibility 241

between the drill steel and the operator. However, despite significant noise reductions
achieved by these controls (up to 6dB in sound power level reduction), many roof-
bolting machine operators are still overexposed from other sources that have now
become dominant. This example suggests the need for continued noise source iden-
tification and ranking, followed by development of additional noise attenuation
controls.
To eliminate the risk of long-term hearing loss, overall noise exposure for mine
equipment operators should be 85dB(A) (NIOSH recommended exposure limit
(REL) for an 8-h shift) or less when possible. Achieving this may require attacking
multiple noise sources simultaneously, resulting in a more comprehensive noise con-
trol methodology. In this context, the approach for future projects will focus on devel-
oping noise controls solutions at the design stage, i.e., quiet-by-design, rather than
localized solutions for existing machines.

References

[1] Masterson EA, Tak S, Themann CL, Wall DK, Groenwold MR, Deddens JA, Calvert GM.
Prevalence of hearing loss in the United States by industry. Am J Ind Med 2012.
[2] Tak S, Calvert G. Hearing difficulty attributable to employment by industry and occupa-
tions: An analysis of the National Health Interview Survey—United States, 1997-2003.
J Occup Environ Med 2008;50:46–56.
[3] Tak S, Davis RR, Calvert G. Exposure to hazardous workplace noise and use of hearing
protection devices among US Workers—NHANES, 1999–2004. Am J Ind Med
2009;52:358–71.
[4] Kirkup SM. The boundary element method in acoustics. Heptonstall: Integrated Sound
Software; 1998.
[5] Marburg S. Chapter 11, Discretization requirements: how many elements per wavelength
are necessary? In: Marburg S, Nolte B, editors. Computational acoustics of noise propa-
gation in fluids. Berlin, Heidelberg, Germany: Springer-Verlag; 2010.
[6] Langley RS, Bremner P. A hybrid method for the vibration analysis of complex structural-
acoustic systems. J Acoust Soc Am 1999;105(3):1657–71.
[7] Shorter PJ, Langley RS. Vibro-acoustic analysis of complex systems. J Sound Vib
2005;288(3):669–99.
[8] Shorter PJ, Langley RS. On the reciprocity relationship between direct field radiation and
diffuse reverberant loading. J Acoust Soc Am 2005;117(1):85–95.
[9] Mueller TJ, editor. Aeroacoustic measurements. Berlin, Heidelberg, Germany: Springer-
Verlag; 2002.
[10] Camargo HE. A frequency domain beamforming method to locate moving sound sources.
Doctoral dissertation, Blacksburg, VA, USA: Virginia Polytechnic Institute and State Uni-
versity; 2010. May 4.
[11] Camargo HE, Burdisso RA. A frequency domain technique to de-dopplerize the acoustic
signal from a moving source of sound. Proceedings of the 17th AIAA/CEAS aeroacoustics
conference, Portland, OR, USA, June 6-8; 2011.
[12] Brooks TF, Humpreys WM. A deconvolution approach for the mapping of acoustic
sources (DAMAS) determined from phased microphone arrays. J Sound Vib
2006;294:856–79.