mestone min g - is it noisy or not? 

Introduction E.R. BAUER AN0 O.R. BABlCH exponentially with age until age 50, at 

Noise is present throughout the which time 60 percent to 90 percent 

mining industry. Continued exposure to LA. Bauer,loemler SMLandDfl. hbii anminiu of the miners had a hearing impair- high noise levels (NIOSH recommend- enuineenwlme WaionallnsliMefor OccuualionalSafeV ment (NIOSH, 1996b, 1997). 

ed exposure limit (REL) of 85 dB(A) rnnlM~[INIOSH\,PinsbnrehhPR.Pape~u~~1~a5010. Despite extensive work with enas a eight-hour time-weighted average Onginalmanustnotsnb~insdonlineAuunsl2005.Re~ised gineering controls in the 1970s and 

(TWA) (NIOSH, 1998)) can cause dam- manuscriptacceotelfor ~uhlica~onJannary2006.Oiscussion 1980s, NIHL is still a problem in the 

age to the inncr car.The eventual result ol!n:s)ee~.~e~~e,~edanlao~m,edoa~srs nileomon.sl mining industry (~ederal Register, 

is a permanent shift in hearing thresh- besihnne(loS11tP~nn0t~l.~loJan.3l.~. 1996).To address this issue, the U.S. 

olds. which is known as noise-induced Mine Safctv and Health Adminishearing loss (NIHL). NIHL. is the most 

common occupational disease in the United States today, 

with 30 million workers exposed to excessive sound levels 

or toxicants that are potentially hazardous to their hearing (NIOSH, 1996a). l%e problem is particularly severe 

in all areas of mining (surface, processing plants and underground) where large, noisy equipment predominates. 

Studies indicate that 70 percent to 90 percent of all miners have NIHL great enough to be classified as a hearing disability (NIOSH, 1996b). An analysis of NIHL in 

miners presents a snapshot of the extent of NIHL in the 

mining industry (Fig. 1) (NIOSH, 1996b).This analysis of 

a private company's 20,022 audiograms indicates that the 

number of miners with hearing impairments (dehed as 

an average hearing threshold level of 25 dB or greater for 

the frequencies 1,000,2,000, 3,000 and 4000 Hz) increased 

tration (M~HA) published "Health 

Standards for Occupational Noise Exposure" (Federal 

Register, 1999). Requirements of the new regulation include the adoption of a hearing conservation program 

similar to that of the U.S Occupational Safety and Health 

Administration (OSHA), with an "Action Level" of 85 

dE3(A) eight-hour time weighted average (TWA,) and a 

permissible exposure level (PEL) of 90 *A) WA,. The 

new regulations also state that a miner's noise exposure 

measurement shall not be adjusted because of the use of 

personal hearing protection, and the requirement to use 

all feasible engineering and administrative controls for 

noise exposure reduction. 

In an attempt to reduce NIHL in the mining industry, 

NOSH researchers have been conducting noise surveys 

in mining, including the limestone industry. The surveys 

Abstract FIGURE 1 

U.S. National Institute for Occupa- Hearing impairment in coal miners, matallnonmetal miners and non-exposed tional Safety and llealrh (NIOSH) males (males that naver worked in the mining industry) (NIOSH, 199613.19971. 

researchers are conducting a cross- roo sectional survey of equipment noise 

and worker noise exposures in the 

mining industry. Surface and undereround limestone is one commodity ., .- f J recently surveyed. The sound leveis 70 1-. - . of mining aand.processing equipment 

were recorded to identify noise sources. Full-shift worker noise exposures 

were completed to determine the exposure of various occupations. This 

article presents the results of the noise 

research conducted in both underground and surface limestone mines, 

detailing the equipment likely to cause 

worker overexposures, and the occupations experiencing overexposures. 

Implications for worker noise exposure reduction are also reported. 
FIGURE 2 l'lGURL 3 

Sound level meters. Location of the dosimeter outside of the haul truck. 

- - -- - -- - are designed to monitor workcr dose, measure equipmt.,, 

Joy Axivane fan in underground limestone mine. sound levels. and to understand the noise source/worker I dose relationship. This was accomplished through fullshift dosimetry readings, equipment noise profiles, and 

where possible, worker task observations. 

Scope of research 

Background. Noise surveys were conducted in one 

surface and three underground limestone mines located 

in eastern and western Pe~sylvania and in northern 

Maryland. In total, 43 worker noise exposures (MSHA 

PELS) and 71 equipment noise profiles were completed. 

Noise exposure measurements were taken for equipment 

operators, crushing plant operators, crusher operators, 

drill operators, scaler operators, blasters, mechanics and 

laborers The equipment noise profiles included stationary and mobile underground and surface mining equipment, control rooms and crushing and screening facilities. 

In addition, the mobile equipment was monitored for 

noise (dose) inside and outside the cabs simply to delineate the effectiveness of the cabs to protect the operaTahl~! 1 tors from engineloperational noise . . 

exposure. MSHA PEL noise dose for limestone mine workers. 

Instnunentabion rurd data coUection. The instrumentation consisted 

of recorded MSHA PEL dose, NlSHA PEL dose, 

PWfenZ pesPem 

55 92 to 187.54 

59.04 to 2W.79 

293.74 to 487 26 

162.32 to 208.96 

truck operator 1 35.89 ND' 

5.85 to 13.36 ND 

erhlaster helper 4 13.27to 2864 ND 

0.90 ta 32.30 ND 

erbborer2 5 17.50 to 119.272 ND 

8.94 NO 

of two basic sound monitoring instruments: personal dosimeters and 

sound level meters (SLM). Worker 

noise exposure was monitored using Quest' Q-400 Noise Dosimeters. 

The workers donned a dosimeter 

for their full work shifts. The microphone was located at the middle of 

the shoulder per MSHA recommen- 

'Reference to brand names does 

not imply endorsement by NIOSH. 
FIGURE 5 FIGURE 6 

Sound contour plot for Joy Axivane tan. Sound contour plot for face drill. 

dations (CFR, 1998). The dosimeter was set to monitor 

an MSHA PEL of 100 percent or a TWA, of 90 &(A). 

(Specific parameters of this setting include A-weighting, 

90 Wthreshold and criterion levels. 5- 

6nnly supported by scientific evidence for assessing hearing impairment as a function of noise level and duration 

(NIOSH, 1998). Measurements collected using a 3-dB exchange rate will result in slightly higher measured sound 

levels than if the MSHA noise standard requirement of a 

5-dB exchange rate were used. A slow response rate with 

an averaging time of 10 seconds was employed, with most 

readings being recorded over a 30-second period. 

Mine eharacteristics. The four limestone mines surveyed included one surface and three underground mines 

A similar mining sequence was used at all the mines. l%e 

sequence included drilling the face or bench, blasting 

the rock and extraction using front-end loaders and haul 

trucks'lle blasted material was transported to the crushDExchmgerate, slow response and a Table 2 

140 cU3 upper limit.) J 

Equipment noise profiles and area Sound level measurements at limesione mines suweyed. 

sound levels were recorded using a 

Quest Model 2900 SLM in combination with a Bruel & Kiaer 2260 Investigator.The SLM and investigator were 

mounted side-by-side on a tripod (Fig. 

2), with the microphone 1.5 m (5 ft) 

from the mine RO& (approximate car 

height), angled at 70E from the source 

(per manufacturer recommendations), 

and facing the sound source. Measurements were made on a 1- to 2-m (3- to 

6-ft) pid at a distance of approximately 1 6 2 m (3 to 6 ft) fromthe equipment. Sufficient measurements were 

made to delineate the sound levels 

both near and far from the equipment. 

The instruments were set up to monitor the A weighted linear equivalent 

continuous sound pressure level (Leq), 

a linear one-third octave band freauencv noise soectrum. a Linear Lea 

ind a k-weighted sound level. Of mosi 

importance was the Leq sound level, 

in decibels (dB), which is the average 

Tamrock Rbnger 500 floor dnll UG 91 to 102 

- Qldsnburg Camon fa^ ar II UG 93 to 103 

Gamner Denver MK~~H face drtll UG 88 to 109 

Gradall XL4300 II scaler UG @to94 

Bbmen bucket truck UG 76 m 81 

sound level for a measurement period 

based on a 3-dB exchange rate.The 3- 

dB exchange rate is the method most 

f 
ing and screening facilities where it was processed into 

various sized aggregate for use in concrete and asphalt 

production, or for sale to end users. Mine production 

ranged from 318 kt/a to 1.36 Mt/a (350,000 to 1.5 million 

stpy) of raw product, or 1.27 kt to 8.1 kt/d (1,400 to 9,000 

stpd). Employment at the mine sites ranged from 10 to 43 

employeesThe underground mines would be considered 

large opening, with heights in excess of 6 m (20 ft) and 

widths in excess of 12 m (40 ft). Underground equipment was both diesel and electric powered. No belts or 

crushers were located underground, but all mine sites had 

crushers, screens and surface belt facilities 

Results 

Worker noise exposure. Workers at each site wore 

dosimeters for a full shift to provide noise exposure data. 

Table 1 lists the worker doses measured, including the 

outside cab doses for evaluation of cab effectiveness in 

preventing exposures from engine noise and equipment 

operation. A typical dosimeter location for outside cab 

measurements is shown in Fig. 3. 

Bvo general conclusions can be made from these data. 

First, all worker doses were below the MSHA PEL of 100 

percent (0.34 percent to 64.21 percent,Table 1) except for 

one of the laborers (119.27 percent). This worker spent 

a simificant ort ti on of the shift usine 

UQUM 7 an &wrenci to tighten bolts while in: 

Nordberg cone crusher. stalling a sheet metal protective canopy at the drift mouth. His exposure 

included not only the air wrench and 

compressor, but also the mobile equipment entering and exiting the mine. 

Secondly, a comparison of the interior 

and exterior mobile equipment doses 

indicates that the equipment cabs are 

providing sufficient protection from 

noise for the operators. 

Equipmenffaree noise measoremen& Sound level measurements were 

taken around all stationary equipment 

such as belts and belt drives, crushers, 

screens, ventilation fans and around 

semistationary mobile equipment, including scalers and face and floor drills 

Table 2 lists the results of the soundlevel measurements for both the surface and underground equipment. 

For convenience, equipment such as 

screens. crushers and belt drives are 

lumped together by category, even 

though they varied widely in size and 

product throughput.The: sound levels 

varied widely because of the size and 

throughput just mentioned, but also 

HGuru (I because of equipment age, size and 

condition and because the ranges in- 

.Sound contour plot for cone crusher. clude measurements taken at varying 

Fd \ distances from the stationary equip- 

/$%\ ment. To illustrate the sound level measurements, several examples are included. Figures 4 and 5 include a 

s<%d photo and contour plot of sound lev- 

,,, 

els around a Joy Axivane fan used for 

2.4 W auxiliary ventilation underground. c Sound levels UD to 105 dBfA) were 

FEET 

recorded adjacent to the fa; and below 90 dB(A) at a distance of approxito3 mately 15 m (50 ft) from the fan. 

Figure 6 is a sound-level contour I plot for a newer (less than 10-years 

old) Oldenbure Cannon face driU.The 

1.. pl~i illustrates-that even at a distance 

of 24 m (79 ft), the sound levels are , 

still 95 dB(A). m'dBw' A Nordberg cone crusher (age 
own) is illustrated in Fig. used underground and on the surface can generate high 

ck from the orimarv sound levels but the cabs are effectivelv shieldine " the ODjaw crusher. The contour plot illustrates that sound levels from 100 to FIOUlll 106 dB(A) were present on the platform around the crusher (Fig. 8). A Doublescreens. 

ing and sizing facilities for one of the 

underground mines. Figure 12 is the I 

sound contour plot for this area, with 

all measurements made at ground level. It illustrates where the hiaher sound I 

levels are and where hear& protection devices (HPD) should be used. I 

Research implications 

Even though only one worker overexposure was recorded,there are some 

important implications of this research 

with respect to NIHL in the mining industry. The differences between dose 

measurements inside and outside the 

mobile eaui~ment cabs suceest that 1 

closed during operation is essential to ~GURE 10 

limiting operator exposure. 

The equipment and area noise Sound contour plot for double sc 

measurements confirm that areas of L 

high soundlevels are present in underground and surface limestone mines. 

As such. hi& sound areas should bc 

~learl~~&~{&.d., workers should 

bqnada~ae of these locations and 

shodd.he.-ddto wear hearing 

protection.at.all times when working 

in these.areasrFinallv. there is some go- . ~.. .~ .. 

e~uipm@it@#@$ q&ke fans, drills, 
that a worker will wear consistently 

when noise levels are above 85 dB(A), 

that is comfortable, is inserted andlor 

worn correctly and is kept clean and 

maintained. 

Research now shows that the noise 

reduction rating (NRR) of most HPDs 

must be derated under normal use. 

The NIOSH Noise Criteria document 

(NIOSH, 1998) suggests derating earmuffs by 25 percent, foam plugs by 50 

percent and molded (flanged) plugs 

by 70 percent. Derating is still only a 

I roughguide and actual protection can 

vary. Finally, MSHA noise regulations 

require the wearing of dual protection 

whenever a miner's noise exposure exceeds a TWA8 of 105 dB(A). . 

Disclaimer 

The hdings and conclusions in this 

article are those of the authors and do 

not necessarily represent the views of 

the U.S. National Institute for Occupational Safety and Health. 

erators from the noise. The crushing and grinding faciliJ ties are also noisy but workers seem to limit their activity ~~f~~~~~~~ 

4 in these areas, thus avoiding overexposure. 

% Code of Federal Regulations (CFR), 1996,Title 30, Mineral ~e- highest sound level (109 dB(A)) was recorded sourcesSubchapter O,Part 70.50fi,p.41g. near the underground fans and face drill. 'Ravel near FederdRegisur, 1996,"Health Standards for Occupational Noise these pieces of equipment while they are operating Exposure in Coal, Metal, and Nonmetal Miner Proposed Rule," U.S. be limited and the of ap- Department of Labor, Mine safety and Health Administration, 30 propriate hearing protecti0n.h appropriateHPD is one CFR Parts 56,57,62,70, and 71,Vol. 61,No. 243, 

FIGURE 12 mesday. Dec. 17. 

Federal Regisur, 1999,"Health Standards for 

Sound contour plot for surface facilities. Occupational Noise Exposure: FInal Rule," U.S 

J =dm. )4zhudmwciso. . , 

FEET 

Department of Labor, Mine Safely and Health 

Admioish.ation, 30 CFR Parts 56 and 57 et al., 

Vol. 64,No. 176, Sept.13.p~. 49548-49634. 

NIOSH. 1996a. "Preventing occupahonal 

hearlng loss - a practical guide," I. Franks, 

M.R. Stephenson and C.J. Meny, eds, National 

Institute for Occupational Safety and Health, 

Cmcinnati. OH. DHHS (NIOSH) Publicahon 

96-110,91 pp. 

NIOSH, 1996b. "Analysis of Audiograms 

for a Large Cohort of Noise-Exposed Miners" 

I. Franks, National Institute for Occupat~onal 

Safety and Health, Cmcmnah. OH, Internal RePort, 7 pp. 

NIOSH, 1997, "Prevalence of Hearing Loss 

for Noise-Exposed MetaVNonmetal Mmers," 

I. Franks, National Institute for Occupational 

Safety and Health, Cincinnati, OH, Internal Report. 5 pp. 

NIOSH, 1998, "Cnteria for Recommended 

Standard, Occupational Noise Exposure, Revised Criteria 1998," National Institute for Occupational Safety and Health, Cincinnati, OH, 

DHHS (NIOSH) Publication 98-126,105 pp.