REDUCING NOISE-INDUCED HEARING LOSS IN LONGWALL 

COAL MINE WORKERS: NIOSH’S APPROACH 

ERIC R. BAUER, ELLSWORTH R. SPENCER, ADAM K. SMITH, ROBERTA L. HUDAK 

National Institute for Occupational Safety and Health 

Pittsburgh Research Laboratory 

Hearing Loss Prevention Branch 

Pittsburgh, PA 

ABSTRACT

The National Institute for Occupational Safety and Health (NIOSH) is conducting 

research with the objective of preventing hearing loss in the mining industry. Longwall 

mining is one sector that has received considerable attention. Studies involving the 

monitoring of worker noise exposures, characterizing equipment sound levels and 

dominant noise sources, evaluating engineering noise controls, analyzing hearing 

protection device (HPD) effectiveness, and testing of improved sound level monitoring 

techniques specifically for longwall mining systems, are being conducted. The research 

efforts revealed that stageloader operators are the most exposed longwall workers, with 

the discharge end being the noisiest location along the stageloader. In addition, the 

studies have shown that using stationary dosimeters, coupled with observational data of 

the cutting cycle and worker habits, has the potential for improved monitoring of the 

effectiveness of engineering noise controls. To address the ineffective use of soft foam 

earplugs, a simplified 3-step method was developed for inserting soft foam earplugs. 

Results indicate a 9 dB greater attenuation after training subjects on the 3-step method. 

Finally, muff type HPDs are being evaluated for effects of speech intelligibility in noise. 

The combined results of these studies illustrates that much can and has been done to 

prevent noise-induced hearing loss (NIHL) in the mining industry, especially with respect 

to longwall mining workers. This paper presents an overview of ongoing studies, a 

progress report of results, and the implications for reducing worker noise exposures and 

preventing NIHL in longwall mining workers. 

INTRODUCTION 

Noise, which is any unwanted or undesirable sound, occurs throughout the mining 

industry. Exposure to high sound levels, i.e. hazardous noise levels, over time can result 

in damage to the hair cells of the cochlea [NIOSH, 1998]. The eventual result is a 

permanent shift in hearing thresholds, known as noise-induced hearing loss (NIHL). 

NIHL is the most common occupational illness in the United States today, with 30 

million workers exposed to excessive noise levels or toxicants that are potentially 

hazardous to their hearing [NIOSH, 1996a]. The problem is particularly severe in all 

areas of mining (surface, processing plants, and underground) where large, noisy 

equipment predominates and where many workers are located in close proximity of this 

equipment. A NIOSH analysis of NIHL in miners presented a snapshot of the extent of 

NIHL in the mining industry (Figure 1) [NIOSH, 1996b]. This analysis of several 
thousand audiograms indicate the number of miners with hearing impairments (defined as 

an average hearing threshold level of 25 dB or greater for the frequencies 1000, 2000, 

3000, and 4000 Hz) increased with age until age 50, at which time 49% of the 

metal/nonmetal and 90% of the coal miners had a hearing impairment [NIOSH, 1996b 

and 1997].

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Figure 1 Hearing impairment in coal miners, metal/nonmetal miners, and non-exposed males 

[NIOSH, 1996b and 1997]. 

Despite the extensive work with engineering controls in the 1970s and 1980s, NIHL 

continued to be a problem in the mining industry [Federal Register, 1996]. To address 

the issue, the Mine Safety and Health Administration (MSHA) published Health 

Standards for Occupational Noise Exposure [Federal Register, 1999]. Requirements of 

the new standard included: 

• The adoption of an Occupational Safety and Health Administration (OSHA)-like 

Hearing Conservation Program (HCP); 

• Enrollment in the HCP for workers exposed above an Action Level of 85 dB(A) 

eight-hour time weighted average (TWA8); 

• Reduce worker exposures to or below A Permissible Exposure Level (PEL) of 90 

dB(A) TWA8 or equivalently a dose of 100%; 

• No reduction in noise exposure due to the use of personal hearing protection; and 

• A requirement that mine operators use all feasible engineering and administrative 

controls to reduce noise exposures. 

Longwall mining and longwall section workers are not immune to noise. A compilation 

of MSHA noise survey data for fiscal year 1990 revealed that approximately 40% of the 

total samples taken for longwall occupations exceeded the Permissible Exposure Level 

(PEL) of 100% [Gigliotti et al., 1991]. Ongoing NIOSH exposure measurements 

revealed noise doses up to 786% for longwall coal mining system workers in job 

classifications that included shearer operator, jacksetter (shieldman), longwall foreman, 
and headgate (stageloader) operator [Bauer et al., 2001]. Bauer also reported that the 

sound levels around the longwall ranged from 81 dB(A) to 102 dB(A) and showed that 

the stageloader operator was among the most frequently overexposed longwall coal 

mining system worker, with recorded dose levels ranging from 142% to 386%. 

In an attempt to reduce NIHL in the mining industry, NIOSH has been conducting noise 

research in the mining industry. The research efforts have included surveys designed to 

monitor worker dose; measure equipment noise levels; understand the noise source/dose 

relationship; laboratory studies to analyze hearing loss; hearing protection device (HPD) 

effectiveness and speech intelligibility in noise; improved and consistent insertion of soft 

foam plugs; and in-mine testing of improved sound level monitoring techniques. These 

studies have been completed in underground coal mines including longwall mining 

sections, or have generated results that are directly applicable to longwall mining. This 

paper presents the results of these research efforts designed to minimize and eventually 

eliminate NIHL in the mining industry including longwall mining. The results are 

applicable to the 52 longwalls in 46 operating underground coal mines in the U.S. [Coal 

Age, 2006] and the estimated 1500 to 3000 workers that routinely work on, or 

occasionally visit, longwall mining sections. 

RESEARCH PROGRAM 

Preventing NIHL among mine workers has proven to be a difficult task. MSHA has 

addressed the problem by publishing and enforcing new standards for occupational noise 

exposure that require mine operators to adopt an OSHA-like hearing conservation 

program and does not allow adjusting a miner’s noise exposure measurement for the use 

of personal hearing protection. The new standards require the use all feasible engineering 

and administrative controls for noise exposure reduction. MSHA has also been 

conducting acoustical field investigations at mine sites, in response to issued citations, to 

assist mine operators to lower miners’ noise exposures. Mining companies have been 

active in this endeavor through the testing, evaluation, and implementation of engineering 

noise controls as well as reducing worker exposures through the use of administrative 

noise controls. NIOSH, at the Pittsburgh Research Laboratory, has adopted a multifaceted approach with research efforts addressing: 

1. Exposure source/dose measurement and tracking; 

2. Engineering noise controls;

3. Worker empowerment and education; and

4. Communication in noise and personal protective equipment (PPE) (Figure 2).
Noisy tasks/settings Noisy tasks/settings

Empowerment 

& Education

Engineering 

Controls

Empowerment 

& Education

Exposure Engineering 

Source & Dose Controls

Exposure 

Source & Dose

Communication 

& PPE

25% Reduction 

in Overexposure

(5 years)

Communication 

& PPE

Controls needed

25% Reduction 

in Overexposure

(5 years)

Controls needed

Barriers and needed innovations

Barriers to implementation

Barriers and needed innovations

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(5 years)

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Figure 2 NIOSH/PRL Hearing Loss Program and Goals. 

SCOPE OF RESEARCH 

The worker-dose monitoring, equipment noise profiles, noise source/dose relationship 

determination, and alternative monitoring research efforts were conducted on the 

longwall sections in underground bituminous coal mines. These efforts involved using 

personal dosimeters for monitoring longwall worker dose, sound level meters and/or 

dosimeters to measure longwall equipment noise, and task observations of workers and 

equipment operating parameters to identify the source(s) of worker noise exposure. 

The hearing protection and audibility consideration research efforts are conducted in 

NIOSH PRL’s Auditory Research Laboratory (ARL), which is accredited by the National 

Voluntary Laboratory Accreditation Program (NVLAP). These efforts involve 

investigating speech intelligibility concerns that arise when noise-exposed miners are 

required to wear hearing protection. Laboratory evaluation of the acoustical 

characteristics of various muff-type hearing protective devices, with an emphasis on 

optimizing the balance between under-/over-protection, effectiveness, and 

communication ability, will be conducted on individuals with normal hearing using the 

Modified Rhyme Test [ANSI S3.2-1989, R1999]. Results of these evaluations will allow 

recommendations to be made for accommodating noise-exposed miners so that they can 

perform their jobs safely while still being protected against noise-induced hearing loss. 

Finally, the Roll-Pull-Hold (RPH) method of soft foam earplug insertion was evaluated at 

numerous mine sites and hundreds of mine workers in the NIOSH Mobile Hearing Loss 

Prevention Unit to determine if the RPH technique had an effect on earplug attenuation 

performance. 
RESEARCH RESULTS 

WORKER EXPOSURE MONITORING 

Longwall section workers wore dosimeters for a full shift to provide noise exposure data 

(Table 1) [Babich and Bauer, 2006]. The wide range of exposure data for each 

occupation is a result of many factors including: work habits; worker location; age of 

equipment; equipment operation; and downtime. In addition, Table 1 combines data 

from a number of mines, thus the exposures are the result of different equipment as well. 

Exposure data can be used to reduce NIHL in a number of ways. First, exposure data 

alert mine operators as to which workers are being overexposed and thus which 

occupations need to be addressed concerning exposure reduction efforts. In the case of 

longwall section workers, analysis of data suggests that exposure reduction efforts should 

be directed at essentially all occupations because all experienced exposures in excess of 

the MSHA PEL. Secondly, when exposure information is combined with worker 

observations, administrative noise controls can be implemented more effectively. 

No. of Range of MSHA Occupation Recorded PEL Dose, % Doses 

Tail Shearer Operator 19 22 to 786 

Headgate (Stageloader) Operator 18 36 to 386 

Head Shearer Operator 20 33 to 266 

Longwall Foreman 16 23 to 203 

Relief Shearer Operator 2 22 to 193 

Shieldman 44 13 to 192 

Mechanic/Electrician 24 5 to 156 

Table 1 MSHA PEL dose for longwall section workers 

EQUIPMENT/AREA NOISE MEASUREMENTS

Sound levels were recorded around the longwall equipment including the shearer, 

Armored Face Conveyor (AFC), shields, stageloader and belt, and hydraulic pump unit. 

Table 2 lists the results of the sound levels recorded using a Type 2 sound level meter 

(SLM) on 3- to 6-ft spacing and at a distance of approximately 3 to 6 ft from the 

equipment or less depending on clearance between the mine ribs and equipment. The 

SLM was programmed to monitor the A-weighted Equivalent Continuous Sound Pressure 

Level (Leq), in decibels (dB), which 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 predicting hearing impairment as a function of noise 

level and duration [NIOSH 1998]. Table 2 illustrates that measured sound levels of 

longwall equipment can vary significantly and at times can be considered “hazardous 

noise levels”. 
Equipment Range Leq, dB(A) 

Stageloader and Section Belt 82 to 103 

Hydraulic Pump Unit 74 to 103 

Shearer 85 to 100 

Face (Shields/AFC) 80 to 96 

Table 2 Sound level measurements for longwall section equipment 

To illustrate the sound level measurements, several examples of longwall section 

equipment are included. An illustration of the sound levels around a shearer as it cuts 

from the head to the tail is shown in Figure 3. Sound levels above 95 dB(A) were 

recorded adjacent to the shearer. In response to exposure reduction, this illustration 

reveals that if the head drum shearer operator remains positioned 10 ft or more outby 

(towards the head and stageloader) the head drum, the sound levels are less than 

90 dB(A). This is a location where the sound levels are “safer” thus for an eight-hour 

shift and if the head shearer operator has no other exposure sources, his dose would be 

less than the MSHA PEL of 100%. The tail drum shearer operator needs to be positioned 

as far toward the head as possible, or at least at the middle of the shearer, to minimize 

noise exposure. Even at the midpoint of the shearer where noise levels are between 90 

and 95 dB(A), the operator is likely to be overexposed. Operator repositioning should 

only be employed until appropriate engineering controls can be implemented to reduce 

the noise levels generated by the shearer. 

Figure 3 Sound profile plot for longwall shearer [Babich and Bauer, 2006] 
 Figure 4 is a sound profile plot for a longwall stageloader. Sound levels above 95 dB(A) 

were recorded adjacent to the stageloader and below 85 dB(A) along the belt at distances 

greater than 15 ft from the tailpiece. Exposure reduction can be accomplished by either 

quieting the noisy areas (crusher and tailpiece) with engineering noise controls, or 

through administrative controls that require the stageloader operator to avoid the two 

noisiest areas (crusher and tailpiece areas). Positioning the controls and computer 

monitor on the monorail along the belt and away from the tailpiece can also limit the 

stageloader operator’s exposure. 

Figure 4 Sound profile plot for a longwall stageloader

 Finally, even though exposure durations are low, overexposure may be possible if 

sufficient time is spent near the hydraulic pump car assembly. Sound levels exceeding 95 

dB(A) can be present as illustrated in Figure 5. All mine workers should limit their time 

near the longwall hydraulics to walking past the area at the start and end of each shift. 

When required to walk past or work near the longwall hydraulics, workers should wear 

appropriate hearing protection and perform as much maintenance as possible when the 

system is off. 
Figure 5 Sound profile plot for longwall hydraulics 

NOISE SOURCE/DOSE RELATIONSHIP 

A combination of dosimetry and task observations was used to attempt to estimate the 

noise source/dose relationship. By observing the tasks and locations of longwall workers, 

then matching the observations to the accumulated dose, the tasks and/or locations most 

responsible for a workers dose can be determined. For instance, a stageloader operator 

was observed, his dose measured, then combined into a cumulative dose plot as shown in 

Figure 6. The plot illustrates that the stageloader operator experienced a generally 

uniform dose accumulation throughout the shift with occasional periods of low dose as 

shown by the flat slopes of the cumulative dose line. These low dose periods occurred 

when the worker was along the face and when the stageloader was idle. Other 

observations have shown less dose accumulation occurred when the worker was at the 

controls (located down the belt away from the stageloader) and when along the belt in 

general. Knowledge of the dose accumulation and worker tasks and/or locations can help 

mine operators to implement exposure reduction efforts where they will be most 

effective. For instance, from 1:50 pm to 2:20 pm when the stageloader operator was near 

the head drive, he received approximately 35% of his total shift dose. By limiting or 

eliminating the time working near the head drive the stageloader operator could have 

reduced his final shift dose to approximately 105%. With a few more judiciously 

selected administrative controls (worker repositioning to lower noise areas), the 

stageloader operator could easily reduce his shift dose to below the MSHA PEL of 100%. 
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Figure 6 Cumulative dose plot and task observations for a stageloader operator [Bauer, et al, 2001] 

ALTERNATIVE MONITORING METHODS 

A study was conducted to evaluate an alternative monitoring method for identifying the 

noise sources that are major contributors to the noise exposure of longwall coal mining 

system workers and to evaluate the effectiveness of engineering noise controls to reduce 

the noise source sound levels and exposure of the workers. The measurement system 

used to analyze the noise sources included stationary dosimeters in a documented 

repeatable pattern (locations along the stageloader) and a time-motion study of the cutting 

cycle and stageloader operator’s work cycle [Spencer et al., 2007]. These measurements 

were conducted on the stageloader only. No attempt was made to use this measurement 

system to monitor sound levels on the face (shearer, pan line, shields, or tailgate). This 

would have required a much larger effort than budgetary and personnel constraints would 

have allowed. 

To locate the stationary dosimeters, the stageloader was divided into a number of separate 

measurement segments or areas as shown in Figure 7. The dosimeter locations were 

marked and recorded with reference numbers. The 12 pre-programmed dosimeters were 

attached to magnetic stands then placed at the predetermined locations [Spencer et al., 

2006]. While the dosimeters recorded noise information, researchers conducted the timemotion study of the operator’s work cycle and shearer cutting cycle for the desired 

number of complete passes (a pass consisted of the shearer cutting down to the tailgate 

and back), or cutting cycles of the longwall mining system [Spencer et al., 2007]. 
105-111 dB(A) 87-104 dB(A) 95-105 dB(A) 85-100 dB(A)

80-90 dB(A)

Figure 7 Segments of the longwall headgate mining system and location of stationary dosimeters (not 

to scale) [Spencer et al., 2007] 

The underground measurements revealed that the highest Leq sound levels occur at the 

stageloader discharge segment and tailpiece controls, ranging from 105 to 111 dB(A). 

They remained at about these same levels throughout the test. The studies suggest that 

the use of stationary dosimeters and time-motion studies are a promising method for 

analyzing the effectiveness of engineering noise controls for reducing longwall worker 

noise exposures. 

HEARING PROTECTION AND AUDIBILITY CONSIDERATION 

A research effort is underway in PRL’s Auditory Research Laboratory to evaluate active 

hearing protection devices for effects on speech intelligibility in industrial noise 

environments, particular mining. In addition to protection from noise-induced hearing 

loss, many workers require good speech intelligibility for the safe performance of their 

jobs. Unfortunately, hearing protectors cannot selectively attenuate the noise while 

leaving the speech unaffected. The study is exploring the differences (if any) between 

speech intelligibility measures and signal perception obtained with active cancellation 

earmuffs, electronic amplitude sensitive earmuffs, and conventional passive-attenuation 

earmuffs. Results of these evaluations assist where recommendations must be made for 

accommodating noise-exposed miners, including longwall section workers, so that they 

can perform their jobs safely while still being protected against noise-induced hearing 

loss. 
SOFT FOAM EARPLUG INSERTION STUDIES 

The recommended steps for reducing worker noise exposure include the implementation 

of all feasible engineering noise controls (removing the noise) or administrative noise 

controls (removing the worker). During the process of implementing these controls, if 

the noise levels remain above 90 dB(A), hearing protection devices (HPDs) provide what 

is perceived as an inexpensive way to prevent hearing loss both on and off the job. They 

are worn to reduce the level of sound entering the ear, not to eliminate the sound 

completely. For HPDs to be effective, they must be worn correctly and fit properly. 

Even if a worker does wear hearing protection, they often do not wear it correctly (Figure 

8). 

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Likely protection as worn by worker

Amount of protection (NRR) listed on the box

Figure 8 Mean real-world field test results vs. labeled noise reduction rating (NRR) values for 

seven different earplugs [Berger et al., 1996] 

In response, NIOSH developed a 3-step method for inserting soft foam earplugs. The 

goal of this research effort was to improve the worker’s ability to insert a plug correctly, 

and ultimately reduce hearing loss if the plug is worn correctly and consistently when 

exposed to noise at or above 85 dB(A). The Roll-Pull-Hold (RPH) Hearing Protection 

Method instructs workers how to insert earplugs effectively (Figure 9). This insertion 

method, with simplified instructions, allows the employee to practice inserting earplugs, 

while obtaining training and feedback on their insertion technique. Subjects who 

followed the RPH steps correctly achieved 9 dB higher attenuation than the subjects who 

did not perform the steps correctly. The effectiveness of insertion was evaluated by preand post-insertion audiometric examinations. The worker was ultimately informed that 

soft foam earplugs can be worn consistently and correctly to prevent hearing loss. 
 

Figure 9 Roll-Pull-Hold hearing protection method [NIOSH, 2007]

IMPLICATIONS FOR PREVENTING NIHL 

The combination of research efforts being conducted by NIOSH are designed to reduce 

the incidence of NIHL in mining, including longwall section workers. Information 

gained from full-shift worker exposure monitoring alerts mine management as to which 

workers are being overexposed and which occupations should be addressed concerning 

exposure reduction efforts. When exposure information is combined with worker 

observations, the noise source/dose relationship can be defined. This information allows 

mine operators to implement effective administrative noise controls. Equipment and area 

sound level measurements can be used to generate sound profile plots. These plots can 

alert mine operators and workers concerning the “noisy” areas that should be avoided and 

where engineering noise controls are most needed. 

The alternative monitoring method, although still in the development stage, may prove to 

be an effective way to determine the noise sources responsible for longwall worker 

exposures. It may also prove to be an improved monitoring method for analyzing the 

effectiveness of engineering noise controls on longwall and other mining equipment. 

Finally, the hearing protector and audibility consideration research will assess the 

effectiveness of new technological advances in hearing protection and identify methods 

to improve the audibility of important sounds while wearing hearing protectors. In 

addition, the Roll-Pull-Hold method will promote the correct and consistent use of soft 

foam earplugs. The results of these research efforts will benefit the workers in that they 

can perform the job safely, prevent accidents, and reduce noise-induced hearing loss. 

SUMMARY 

The National Institute for Occupational Safety and Health is spending considerable time 

and effort to reduce noise-induced hearing loss in the mining industry including longwall 

mining. These efforts include the development of engineering noise controls, advancing 

the use of administrative noise controls, exposure and noise measurement, laboratory 
studies to better understand hearing loss and prevention methodologies, hearing 

protection device effectiveness studies, and improved sound level monitoring techniques. 

They are intended to assist both mine operators and individual workers to recognize and 

avoid noise exposures, and effectively protect their hearing. Individually the research 

efforts are just one piece of the puzzle and will not totally eliminate NIHL. Eventually 

when the results of all the efforts are available to the mining industry, NIHL will be 

significantly and positively impacted. 

To date, the most promising results have come from the worker exposure monitoring and 

soft foam earplug studies. The dose monitoring revealed that the stageloader operator 

and shearer operators are the most exposed workers and most likely to experience NIHL. 

The studies have also shown that stageloader operators need to stay away from the 

stageloader discharge area, head drive, and crusher area to minimize their exposure. In 

addition, the shearer operators should stay as far outby (toward the head) as possible to 

minimize their exposure. The soft foam earplug investigations, coupled with training in 

the Roll-Pull-Hold 3-step insertion method, have shown miners that with correct insertion 

they can obtain a 9 dB greater attenuation. The result is less likelihood of developing 

either a temporary threshold shift or a permanent threshold shift (NIHL). The remainder 

of the research efforts addressed in this paper, although still in the early stages, show 

considerable promise in reducing NIHL among longwall workers. Avoiding noise 

exposures, implementing noise controls, and using HPDs effectively will minimize, and 

eventually eliminate, NIHL in the mining industry. 

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Measuring the Intelligibility of Speech over Communication Systems. ANSI S3.2-

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Babich, DR and ER Bauer [2006]. Summary of longwall and continuous miner section 

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