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Measurement method for determining absorption coefficients for underground mines.

Authors
Kovalchik-P; Matetic-R; Peng-S; Cole-G
Source
Min Eng 2007 Nov; 59(11):59-62
NIOSHTIC No.
20032852
Abstract
Previous studies conducted by the National Institute for Occupational Safety and Health (NIOSH) have shown that approximately 90 percent of coal miners and 49 percent of metal/nonmetal miners had a hearing impairment by age 50. Mine workers are exposed to additional noise levels underground due to the reflection of machine generated noise that would otherwise dissipate in an above ground setting. Determining the sound absorption coefficients is essential in modeling the sound field in an underground mining environment. Sound absorption is a measure of the amount of acoustic energy that strikes a surface and is absorbed, rather than reflected. The acoustic environment that mining machines operate in is a critical factor affecting the sound pressure level exposure for mining machine operators. Impedance tube testing is an inappropriate method for determining underground absorption coefficients due to the brittle composition of some of the materials such as coal and slate. Classic absorption coefficient estimation using T60 measurements will not work well in an underground environment because the theory assumes: a finite room, a diffuse field, and relatively uniform absorption. None of these assumptions are true in an open-ended mine entry. This paper will present a method using a ray-tracing technique to determine absorption coefficients for underground mines. Absorption coefficients are determined and presented for octave bands from 63 Hz to 8 kHz. The absorption coefficients will be essential for determining and predicting potential overexposure to machine operators in different mine environments.
Keywords
Mining-industry; Noise; Noise-exposure; Noise-control; Noise-induced-hearing-loss; Coal-mining; Metal-mining; Nonmetal-mining; Underground-mining; Underground-miners; Miners; Mining-equipment; Noise-measurement; Sound-propagation; Sound-attenuation; Acoustic-absorption; Acoustical-measurements; Acoustics
CODEN
MIENAB
Publication Date
20071101
Document Type
Journal Article
Fiscal Year
2008
NTIS Accession No.
NTIS Price
Issue of Publication
11
ISSN
0026-5187
NIOSH Division
PRL
Source Name
Mining Engineering
State
PA; WV
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