T e c h n i c a L P a e r 

Mining Engineerin  November6 

Introduction

Prolonged exposure to noise can 

result in permanent damage to the auditory nerve and/or its sensory components. This irreversible damage, known 

as noise-induced hearing loss (NIHL), 

makes it difficult to hear and understand speech. NIHL is the most common occupational disease in the United 

States today, with approximately 30 million workers exposed to excessive noise 

levels or to toxic agents that are potentially hazardous 

to their hearing (NIOSH, 1996a). The problem is particularly severe in all areas of mining (surface, processing 

plants and underground), with studies indicating that 70 

percent to 90 percent of all miners have 

NIHL great enough to be classified as 

a hearing disability (NIOSH, 1996b). 

An early analysis of NIHL in 1,500 coal 

miners revealed an alarming prevalence 

of severe hearing loss, as shown in Fig. 

1 (NIOSH, 1976). For example, by age 

60 more than 70 percent of the miners 

studied had a hearing loss of more than 

25 dB, and about 25 percent had a hearing loss of more than 40 dB. 

In addition to government researchers, Weeks (1995) reported that the 

policies and practices for preventing 

occupational hearing loss among miners are inadequate and noted that there 

are deficiencies in nearly every sector: 

surveillance of exposure or of outcome, 

analysis and intervention. A more recent 

analysis of NIHL in miners showed an 

apparent worsening of NIHL, as shown 

in Fig. 2 (NIOSH, 1996b). This analysis 

of a private company’s 20,022 audiograms for 3,449 coal miners indicated 

that the number of miners with hearing impairment increased exponentially 

with age until age 52, at which time 90 

percent of the miners had a hearing 

impairment. NIOSH defines hearing impairment as an average hearing 

threshold level of 25dB or greater for 

the frequencies 1,000, 2,000, 3,000 and 

4,000 Hz (NIOSH, 1996b, 1997).

The Federal Coal Mine Health 

Summary of longwall and continuous 

miner section noise studies in 

underground coal mines

D.R. Babich and E.R. B

D.R. Babich and E.R. Bauer, member SME, are mining 

engineers with the National Institute for Occupational Safet

and Health (NIOSH), Pittsburgh Research Laboratory, Pittsbur

PA. Paper number 05-312. Original manuscript submitted Apri

2005 and accepted for publication March 2006. Discussion of 

this peer-reviewed and approved paper is invited and must be 

submitted to SME Publications Dept. prior to Feb. 28, 2007.

Abstract

Noise-induced hearing loss (NIHL) in 

mine workers, especially underground 

coal miners, continues to be a problem 

in the mining industry. The recently 

enacted MSHA noise standard, Part 

62 – Occupational Noise Exposure 

(Federal Register, 1999), is aimed at reducing NIHL in the mining industry. 

The U.S. National Institute for Occupational Safety and Health (NIOSH) 

is conducting a cross-sectional survey 

of noise sources and worker noise 

exposures to address NIHL in various aspects of coal mining including 

surface mining, coal preparation 

plants and underground mining. In 

underground bituminous coal mining, 

noise surveys, consisting of full-shift 

worker noise exposure, time-motion 

studies and equipment noise profiling, have been completed on longwall 

and continuous miner sections in six 

underground coal mines. The studies 

revealed widely varying shift-to-shift 

worker exposures, with workers in 

certain occupations routinely exposed 

to potentially hazardous levels of 

noise. A summary of these studies 

is reported, including worker dose, 

source/dose relationships and equipment noise profiles.

and Safety Act of 1969 established 

requirements for protecting coal 

miners from excessive noise. Subsequently, the Federal Mine Safety 

and Health Act of 1977 broadened 

the scope to include all miners, regardless of mineral type (Code 

of Federal Regulations [CFR] 30, 

1997). Since the passage of these 

Acts, there has been some progress 

in controlling mining noise. In fact, 

data from more than 60,000 full-shift MSHA noise surveys show that, in general, the noise exposure of selected 

occupations has decreased since the 1970s (Seiler et al., 

1994). However, for these same surveys, the percentage 

of coal miners with noise exposures 

exceeding federal regulations, unadjusted for the wearing of hearing 

protection, was 26.5 percent and 

21.6 percent for surface and underground mining, respectively (Seiler 

et al., 1994).

Despite the extensive work with 

engineering controls, education and 

hearing conservation in the 1970s 

and 1980s, NIHL is still a pervasive 

problem in the mining industry 

(Federal Register, 1996). MSHA recently published new Noise Health 

Standards for Mining (Federal Register, 1999), and one of the changes 

is the adoption of a provision similar 

to OSHA’s Hearing Conservation 

Amendment. MSHA concluded in 

a recent survey that if an OSHAlike hearing conservation program 

were adopted, hypothetically, 78 

percent of the coal miners surveyed 

would be required to be in a hearing conservation program (Seiler 

and Giardino, 1994). Other requirements of the new regulations are a 

permissible exposure level (PEL) of 

90 dB(A) TWA8 (which stands for 

time weighted average – 8 hour and 

is defined as the sound level that if 

constant over 8 hours would result 

in the same noise dose as is measured [Federal Register, 1999]); no 
credit for the use of personal hearing protection; and the 

primacy of engineering and administrative controls for 

noise exposure reduction.

Complicating the problem of NIHL in mining, much 

of the existing noise and worker-exposure information is 

outdated and has limited value for current research and 

engineering control decision-making. In many cases, the 

data are specific to machine type and were obtained for 

characterizing noise sources rather than exposure assessment. There is also a great range in noise levels for a given 

occupation. For example, noise levels for continuous miner operators range from 80 to 105 dB(A) (MSHA, 1997). 

As determined using the new Noise Health Standards, a 

noise level of 80 dB(A) translates into a daily noise dose 

of 0 percent, while a 105 dB(A) level represents a daily 

noise dose of 800 percent. 

Yet, at present, there is insufficient information to 

explain this great variation in exposure for this and other 

mining occupations and an understanding of this variability is necessary to identify appropriate solutions. Specifically, noise level data are needed that provide a time 

exposure history for workers in addition to further information on noise sources. This information will provide 

the basis for targeting and selecting engineering controls, 

in combination with administrative controls, and the use 

of personal protective equipment, to reduce noise exposures among the mining workforce.

Scope of research

This research effort was conducted at six underground 

coal mines located in Alabama, Colorado, Pennsylvania 

and West Virginia. Thirty-three shifts were spent collecting approximately 333 worker noise exposures, 43 worker 

task observations and 80 equipment noise profiles. Worker 

noise exposure was monitored using Quest Q-400 Noise 

Dosimeters, which were configured 

to monitor the MSHA Permissible 

Exposure Level (PEL) (TWA8 of 

90 dB(A), or equivalently a dose 

of 100 percent). Task observations 

were conducted for workers who 

routinely experienced noise exposures above the MSHA PEL.

The equipment noise profiles, 

which were made using a Quest 

Model 2900 Sound Level Meter, 

include both longwall and continuous mining section equipment. 

The measurement recorded was 

the A-weighted linear equivalent 

continuous sound pressure level 

(Leq(A). The Leq(A) in decibels is 

the average sound level for a measurement period based on a 3-dB 

exchange rate. The 3-dB exchange 

rate is the method most firmly supported by scientific evidence for 

assessing hearing impairment as a 

function of noise level and duration (NIOSH, 1998). Descriptions 

of how these worker dose and 

noise profiles were obtained and 

the types of equipment measured 

are included below.

Results

Summaries and representative examples of data collected 

are presented that include worker 

dose, task observations keyed to 

Table 1 

Occupations experiencing noise exposures, arranged by percent doses of more 

than 132 percent.	 	 	 	 	 	

	 	 	 	 	 	 Doses greater Doses

Range than MSHA PEL greater 

Occupatons (sample size) of dose, % of 100%, % than 132%, %

Longwall:

Shearer operator (37)	 22-786

	 73	 62

Headgate/stageloader operator (15)	 36-386	 73	 53

Relief shearer operator (2)	 22-193	 50	 5

Shieldman/jacksetter (35)	 13-192	 40	 2

Foreman (14)	 23-203	 36	 14

Electrician/mechanic (21)	 5-156	 33	 

Continuous mining:

Roof bolter operator (16)	 57-355	 81	 6

CM operator/helper (14)	 43-347	 86	 57

Miner/bolter roof bolters (30)	 9-275	 60	 40

Utility man/faceman (37)	 6-297	 32	 22

Miner/bolter operator (14)	 45-195	 64	 21

Foreman (16)	 17-232	 31	 19

Shuttle car operator (31)	 9-165	 16	 

Mechanic/electrician (18)	 4-162	 6	 6

Ram car operator (4)	 83-122	 25	 

Loading machine operator (12)	 25-81	 0	 0

Center bolter operator (17)	 17-57	 0	 0

1

786 percent — No noise level at or above 105 dB(A) was recorded at the worke

locations for this person (note: microphone was found pinned to worker’s breast shirt

pocket). The next highest recorded dose for this occupation was 408 percent.

Figure 1 

Hearing loss as a function of age (adopted from NIOSH, 

1976).
cumulative dose plots and sound profile plots of equipment noise. The volume of data collected in this study 

precludes including all results.

Worker dose. Full-shift dosimetry measurements 

(ranging from 8 to 12 hours) were recorded for 333 underground workers primarily engaged in coal extraction 

at the face. The worker dose measurements indicated 

that 42 percent (141 of 333) of the total doses recorded 

were above the MSHA PEL of 100 percent. Of those 

above the PEL of 100 percent, 65 percent (91 of 141) 

were above the MSHA citable PEL of 132 percent (citable level is 132 percent because of 2 dB error of Type 2 

instruments, i.e., 100 percent 2 dB (32 percent)). In other 

words, approximately 27 percent (91 of 333) of the total recorded doses were citable under 

MSHA guidelines. 

Table 1 lists occupations in longwall and continuous mining sections 

and a summary of dose measurements. 

The table illustrates that the range of 

dose within each occupation varies 

considerably. Many of these occupations or job classifications routinely 

experience noise exposures above the 

PEL. These workers are periodically 

subjected to noise levels that have the 

potential to cause NIHL.

Task observations. Workers experiencing doses above the PEL were task 

observed while wearing a dosimeter. 

The task observations (time-motion 

studies) included the duration of the 

tasks the worker performed and his 

location with respect to the equipment 

and/or noise sources. The goal was to 

identify the tasks and associated noise 

sources responsible for the workers 

measured dose and to provide mine 

operators with sufficient information 

to begin implementing noise exposure reduction efforts. A cumulative 

dose plot for a miner/bolter operator, 

with task observations annotated, is 

illustrated in Fig. 3. The rate of dose 

accumulation was greatest (indicated 

by the steep slope of the line) while 

trimming a corner with the conveyor 

running empty, followed by cutting/

bolting/hang tubing at the face. Little 

dose was accumulated while the worker was at lunch and during equipment 

idle times as illustrated by the flat 

slope of the cumulative dose line.

Figure 4 is an example of a cumulative dose plot for a longwall headgate/stageloader operator. The plot 

illustrates that other than during 

equipment idle times, the headgate/

stageloader operator experienced a 

uniform dose throughout the shift, 

with the greatest rate of accumulation 

while working within 1 m (3 ft) of the 

Figure 2 

Hearing impairment in coal miners, non-coal miners and non-exposed males 

(NIOSH, 1996b, 1997).

Figure 3 

Cumulative dose plot for miner/bolter operator.

head drive. The periodic no dose times (flat slopes) occurred when the worker left the headgate to get supplies, 

carry out belt structure and take breaks.

Equipment noise. As noted above, 80 equipment 

noise profiles were completed in underground coal mines. 

Some of these profiles were done on similar equipment 

but in different mines. The equipment profiled included 

continuous mining machines, combination continuous 

miner-bolter machines, roof bolting machines (both dualboom and single-boom center bolter), loading machines, 

shuttle cars, auxiliary fans used at the face, feeder-breakers, electrical power centers, longwall shearers, longwall 

stageloaders and track-mounted longwall hydraulic pump 

car assemblies. Results of the noise profiles for the differ-
Figure 5 

Sound profile plot for longwall shearer while cutting from headgate to tailgate.

Figure 4 

Cumulative dose plot for longwall headgate/stageloader operator.

Table 2 

Range of Leq(A) noise levels measured on a fixed grid 

for continuous mining section equipment.

Range, Measured location of

Equipment dB(A) highest noise Level

Auxiliary fan	 84-120	 Exhaust si

Miner/bolter	 84-112	 At drill station

Continuous miner	 78-109	 Within 5 m (15 ft) of tail

Roof bolter	 92-103	 At drill statio

Feeder/breaker	 81-97	 Discharge end

Shuttle car

	 78-89	 In operator’s cab during

unload

1

Includes drive-by, stationary loading and stationary unloading measurements

ent types of equipment are shown in Tables 2 and 3.

The profile measurements were taken at 1-m (3-ft) 

intervals (grid), starting 1 m (3 ft) from the equipment, 

and included several points above the equipment. Some 

measurements were made closer to the equipment when 

clearance between equipment and rib was less than 1 m 

(3 ft). The readings were taken only when the equipment 

was in operation. Some readings, particularly those at 

the very front of a continuous miner, loading machine 

or longwall shearer, were unable to be taken for obvious 

safety reasons.

For analysis, the noise data collected from around 

the mining equipment were converted to sound profile 

plots. Although space limitations prevent presenting all 

the noise profiles, several examples from both longwall 

and continuous mining sections are included. Figure 

5 is a sound profile plot for a longwall shearer as it is 

cutting from headgate to tailgate. Note that the highest 

noise levels are at the lead drum end 

of the machine when cutting in this direction. The noise levels drop significantly along the machine toward the 

headgate and trailing drum. This figure 

illustrates that, if the head shearer operator is positioned 3 m (10 ft) or more 

outby (the direction away from the 

working face) on the stageloader side 

of the trailing drum, the operators dose 

should be less than the PEL. Likewise, 

the lead drum operator needs to position himself as far away from the lead 

drum toward the head as possible, or 

at least at the middle of the shearer, to 

minimize his noise exposure.

Figure 6 presents a sound profile 

plot for a longwall stageloader and 

panel belt. The highest noise levels 

were found near the crusher, which 

breaks the larger lumps of coal and 

rock, and near the tail piece where the 

stageloader conveyor chain drive motors are located. These are the two areas that the headgate operator, and all 

other longwall workers, should minimize their time spent.

Figure 7 is from a continuous miner 

section and illustrates the noise around 

a dual-boom roof-bolting machine. 

The data were collected during several 

complete bolting cycles. The highest 

noise levels were recorded near the 

right side operator’s location during 

the bolting cycle. Noise levels dropped 

below 90 dB(A) approximately 4 m 

(12 ft) outby the drill.

Finally, Fig. 8 is an example of 

a pair of auxiliary ventilation fans 

located on a continuous mining section. These fans were extremely noisy, 

reaching 118 dB(A) near one fan on 

the inby (the direction toward the 

working face) side of the curtain. Even 

at 14 m (46 ft) inby, the noise level was 

still over 100 dB(A). For any worker 
traveling within this distance, the dose would accumulate 

rapidly, and as such, the area should be avoided when 

possible.

Implications for noise exposure reduction

Although the goal of this research was to coordinate a 

survey of noise sources and worker noise exposures, some 

general implications for reducing worker noise exposures 

can be drawn. The results suggest that workers directly 

involved with coal extraction at the face are most likely to 

experience overexposure to noise. As such, these are the 

occupations where mine operators should concentrate 

their noise control efforts. The occupations that should 

be the first to be included in any noise exposure reduction efforts are the continuous miner and miner/bolter 

operators, miner/bolter roof bolter operators, roof bolter 

operators, longwall shearer operators and headgate/

stageloader operators. As illustrated in Table 1, these are 

the occupations with the highest percentage of recorded 

doses over the MSHA PEL. 

According to the MSHA noise standard Part 62, mine 

operators must use all feasible engineering and administrative controls to reduce the miner’s noise exposure 

below the permissible exposure level (Federal Register, 

1999). Engineering controls reduce noise exposure by 

decreasing the amount of noise reaching a worker. Sound 

profile plots can indicate which equipment is generating the highest noise 

levels, but not what specific component 

of the piece of equipment is responsible. This at least gives mine operators a starting point based on reliable 

and accurate information. Examples of 

engineering controls include maintenance, acoustic isolation or absorption, 

barriers, motor enclosures, fan silencers, modification of machine mounting, mufflers and replacement of noisy 

equipment with quieter equipment. 

Administrative controls reduce exposure by limiting the time a worker is 

exposed to noise. 

By evaluating the cumulative dose 

plots, task observations and sound 

profile plots, the tasks, equipment or 

areas that significantly influence a 

worker’s dose can be identified and 

then modified or avoided to minimize 

exposures. Examples of administrative 

controls include job rotation (switching a worker with high noise exposure 

with someone having less noise exposure), modifying the job or equipment 

operation to reduce exposure to noisy 

areas or equipment, shift length reduction when more than 8 hours, and 

where possible, providing quiet areas 

or areas from which remote monitoring utilizing gauges and/or video can 

take place.

Summary

Overexposure to noise among 

mine workers continues to be a probTable 3

Range of Leq(A) noise levels measured on a fixed grid 

for longwall mining section equipment.

Range, Measured location of

Equipment dB(A) highest noise level

Stageloader	 84-102	 Head drive, crusher

gearboxes and 

bridge co

Shearer	 85-99	 Adjacent to dr

Hydraulic pump car	 78-99	 Motors and pumps

Head drive	 89-96	 At gear box o

shield s

Tail drive	 92-94	 At return escapeway en

Panline	 78-91	 At head driv

Dinner hole	 <60-90	 When located within

	 1.8 m (6 ft) of stageloader

Figure 6 

Sound profile plot for longwall stageloader.

Figure 7 

Sound profile plot of sound levels around a dual-boom roof-bolting machine.

lem for the mining industry. This research effort found 

that 27 percent (91 of 333) of the underground face 

workers studied experienced noise exposures above the 

MSHA citable level of 132 percent, and 42 percent (141 

of 333) experienced doses greater than 100 percent. The 

equipment generating the highest noise levels include 
ring

the stageloader (102 dB(A)) and shearer (99 dB(A)) 

in longwall sections and include the auxiliary fans (120 

dB(A)), miner/bolters (112 dB(A)), continuous miner 

(109 dB(A)) and roof bolting machines (103 dB(A)) in 

continuous mining sections.

The solutions to reducing mine-worker noise exposure 

are many and difficult and will need to include a combination of engineering and administrative approaches. They 

will also include providing additional training and supervision to increase the underground worker’s awareness 

of high noise areas and the beneficial effects of moving 

out or away from those areas when possible. The cooperation of all parties (labor, management, regulatory and 

research community) is necessary if NIHL among mine 

workers is to be reduced and/or eliminated. n

Figure 8 

Sound profile plot for auxiliary fans.

References

CFR 30, 1997, Code of Federal Regulations (CFR) governing noise 

exposure in mining, CFR 30, Subchapter O, Part 70, Subpart F: Noise 

Standards for Underground Coal Mines; Subchapter O, Part 71, Subpart D: Noise Standards for Surface Work Areas of Underground Coal 

Mines and Surface Coal Mines; Subchapter O, Part 55, Section 55.5: 

Metal and Nonmetal Open Pit Mines; Section 56.5: Sand, Gravel, and 

Crushed Stone Operations; 57.5: Metal and Nonmetal Underground 

Mines.

Federal Register, 1996, “Health Standards for Occupational Noise 

Exposure in Coal, Metal, and Nonmetal Mines: Proposed Rule,” Department of Labor, Mine Safety and Health Administration, 30 CFR 

Parts 56, 57, 62, 70, and 71, Vol. 61, No. 243, Tuesday Dec. 17, pp. 66348-

66469.

Federal Register, 1999, “Health Standards for Occupational Noise 

Exposure: Final Rule,” Department of Labor, Mine Safety and Health 

Administration, 30 CFR Parts 56 and 57 et al., Vol. 64, No. 176, Monday, 

Sept. 13, pp. 49548-49634.

MSHA, 1997, “Environmental Noise Report, District Summaries, 

Fiscal Year 1997.”

NIOSH, 1976, “Survey of Hearing Loss in the Coal Mining Industry,” National Institute for Occupational Safety and Health, Publication 

No. 76-172, June, 70 pp.

NIOSH, 1996a, “Preventing Occupational Hearing Loss — A Practical Guide,” J.R. Franks, M.R. Stephenson and C.J. Merry, eds., National 

Institute for Occupational Safety and Health, Cincinnati, OH, DHHS 

(NIOSH) Publication No. 96-110, 91 pp.

NIOSH, 1996b, “Analysis of Audiograms for a Large Cohort of 

Noise-Exposed Miners,” J.R. Franks, National Institute for Occupational Safety and Health, Cincinnati, OH, internal report, 7 pp.

NIOSH, 1997, “Prevalence of Hearing Loss for Noise-Exposed 

Metal/Nonmetal Miners,” J.R. Franks, National Institute for Occupational Safety and Health, Cincinnati, OH, internal report, 5 pp.

NIOSH, 1998, “Criteria for a recommended standard: occupational 

noise exposure, revised criteria 1998,” Cincinnati, OH, U.S. Department 

of Health and Human Services, Public Health Service, Centers for 

Disease Control and Prevention, National Institute for Occupational 

Safety and Health, DHHS (NIOSH) Publication No. 98–126, 105 pp.

Seiler, J.P., Valoski, M.P., and Crivaro, M.A., 1994, “Noise Exposure 

in U.S. Coal Mines,” U.S. Dept. of Labor, Mine Safety and Health Administration, informational report IR 1214, 46 pp.

Seiler, J.P., and Giardino, D.A., 1994, “The Effect of Threshold on 

Noise Dosimeter Measurements and Interpretation of Their Results,” 

U.S. Dept. of Labor, Mine Safety and Health Administration, informational report IR 1224, 16 pp.

Weeks, J.L., 1995, “Policies and Practices for Preventing Occupational Hearing Loss Among Miners are Inadequate,” Proceedings of 

Hearing Conference III/XX, Cincinnati, OH, March, pp. 16-19.

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