Identification of noise sources on 

longwall panels using multiple 

time-synchronized dosimeters

E.R. Spencer, D.R. Babich, L.A. Alcorn and A.K. Smith

Mining engineer, mining engineer, engineering technician and mechanical engineer, respectively, 

National Institute for Occupational Safety and Health (NIOSH), Pittsburgh, Pennsylvania.

Abstract

Noise is one of the most pervasive health hazards in mining. A compilation of Mine Safety and Health 

Administration (MSHA) noise survey data for fiscal year 1990 shows that approximately 40% of the 

total samples taken for longwall occupations exceeded the Permissible Exposure Limit (PEL) of 100% 

(Gigliotti et al., 1991). To effectively determine worker noise exposures on longwall coal mining systems, 

it is necessary to provide accurate baseline measurements for these mining systems. This research was 

designed to develop measurement methods and test procedures for identifying noise sources that are 

major contributors to the underground noise exposure of longwall coal mining system workers. The 

measurement system that was used to analyze the noise sources around a stageloader used stationary 

dosimeters in a documented repeatable pattern to record the sound pressure and dose levels. A timemotion study of the cutting cycle and stageloader operator’s work cycle was done to correlate the sound 

levels at measurement locations and the resulting operator’s daily dose with significant noise events. 

Results from the underground measurements show that the highest sound levels recorded were at the 

stageloader discharge segment and tailpiece controls, where sound levels remained about the same 

throughout the test.

Introduction

Despite 25 years of regulation, overexposure to noise remains 

a widespread, serious health hazard in the U.S. mining industries. Noise-induced hearing loss (NIHL) is the most common 

occupational illness in the United States today, with 30 million 

workers exposed to excessive noise levels (NIOSH, 1999). 

Noise doses (PEL) of up to 786% have been recorded for 

longwall coal mining system workers with job titles such as 

shearer operator, jacksetter, longwall foreman and head gate 

(stageloader) operator (Bauer et al., 2001). This study revealed 

that the sound levels around the longwall mining system ranged 

from 81 to 102 dB(A). The study also showed that stageloader 

operators were among the most exposed longwall coal mining 

system workers, with recorded PEL dose levels ranging from 

142% to 386%. 

This paper presents suggested measurement methods from 

research done by the NIOSH Pittsburgh Research Laboratory to 

reduce noise exposure in mining environments. The measurement methods used identify the noise sources that are major 

contributors to the underground noise exposure of longwall 

mining system workers. The procedures followed allow for 

accurate, repeatable measurements of the noise sources and for 

the development and evaluation of noise controls on longwall 

mining systems. Specifically, this paper concentrates on the 

noise emissions of a DBT America1 longwall stageloader system. DBT America longwall stageloader systems make up approximately 40% of the stageloaders in use in underground coal 

mines (Coal Age, 2006) and thus are representative of industry 

usage. Mining equipment manufacturers, mining companies 

and MSHA intend this information for use for evaluating the 

effectiveness of engineering noise controls.

Background

2004 study. NIOSH researchers completed a study evaluating 

an engineering noise control on a JOY stageloader in New 

Mexico in 2004 (Bauer et al., 2005). The study was performed 

in three phases: precontrol, postcontrol and 6-month postcontrol. The noise control tested included sound-absorptive filled 

cavities on the crusher and gooseneck using bagged fiberglass 

 1 References to specific brand names do not imply endorsement 

by the National Institute for Occupational Safety and Health.
Figure 1 — Segments of the longwall head gate mining system (not to scale) with dosimeter locations.

covered with conveyor belting. The sound levels, worker 

noise exposure levels and four stationary dosimeter measurements were collected at similar locations and conditions for 

all phases. The sound level measurements made in the head 

gate area and along the length of the stageloader were taken 

at 30 locations using a sound-level meter set to average over a 

30-second time period. A minimum 15-minute test period was 

required when mining conditions were constantly changing. 

The 6-month postcontrol sound levels were on average 2 to 3 

dB lower than the initial postcontrol sound levels and nearly 

the same as the precontrol sound levels. Overall, it was not 

possible to determine if the implemented engineering noise 

control reduced the stageloader sound levels or the stageloader 

operator noise exposure.

In this 2004 study, although various types of measurements 

were conducted on the stageloader over several shifts, the test 

results varied and were inconclusive. At this study site, production levels varied greatly because of problems associated with 

hydrogen sulfide (H2S). This resulted in widely varying amounts 

of coal in the stageloader because production was decreased 

or stopped when the concentration of H2S in the environment 

reached a certain level. Thus, changing amounts of the coal 

being cut, crushed and conveyed was a major factor in the 

variability of the testing results. In addition, the movement of 

the longwall face in relation to the crosscuts and the varying 

size of the section caused deviations in the long-term or shift 

measurements. The high percentages of noise overexposures, 

wide ranges of dose levels and the inability to evaluate noise 

controls underground prompted NIOSH to perform follow-up 

research to determine methods and procedures for measuring 

the longwall mining systems underground.

Research approach to current study. In the 2004 study, 

research concentrated on exposure/dosage measurements and 

single sound-level measurements as indicators of excessive 

noise problems on longwall mining systems. The sound-level 

measurements made in the head gate area and along the length 

of the stageloader were taken at 30 locations and took more 

than 15-minutes to complete while mining conditions were 

constantly changing. The current study’s approach to measurement methods included using time-synchronized stationary 

dosimeters for measuring sound levels of the longwall mining 

system and conducting a time-motion study. The time-motion 

study was used in conjunction with sound-level measurements 

to correlate operational events on the longwall stageloader 

mining system with periods of high noise generation. This allowed for repeatable and full-test period measurement of noise 

sources on longwall stageloader mining systems for prenoise 

and postnoise control evaluations.

Permissible dosimeters were used to record the sound levels 

and were placed on the stageloader and in the head gate area 

in a documented pattern (Fig. 1). Because of the size of the 

stageloader, the stationary dosimeters were placed at known 

noise sources on the machinery, (e.g., armored face conveyor 

(AFC), crusher and discharge). The dosimeters were fitted on 

magnetic stands with their microphones approximately 300 

mm (12 in.) from the magnet base. Any height greater than 

this might have resulted in the instruments being knocked off 

or crushed because of the low clearances. Each dosimeter was 

set to record the equivalent sound level every 10 seconds using an exchange rate of a 3-dB, A-weighting, slow response, 

40-dB threshold level and a 140-dB upper limit. Data recorded 

from the dosimeter provided the following information: an 

A-weighted sound pressure level, maximum and minimum 

sound levels, and absolute unweighted peak sound levels at 

each of the designated positions. To obtain the MSHA PEL and 

time-weighted average over 8 hours (TWA(8)), the dosimeters 

were also set to meet MSHA criteria, which included a 5-dB 

exchange rate, A-weighting, slow response, 90-dB threshold 

level, a 90-dB criteria level and a 140-dB upper limit (Code 

of Federal Regulations, 1999). 

Two researchers conducted a time-motion study in conjunction with these measurements. One researcher was positioned 

at the head gate and was responsible for recording the shearer 

position and the status of the AFC (off or running empty, 

half-full or full) with the time of the shearer’s cutting cycle 

and distance from the head gate. The other was positioned at 

the stageloader discharge area and was responsible for the 

stageloader armored conveyor (AC) status (off or running 

empty, half-full or full), the stageloader operator’s position 

and the stageloader movement time and distance moved. The 

dosimeters and the watches used for the time-motion study 

were time synchronized.

Test plan. To determine effective dosimeter locations, distance 

measurements of the longwall stageloader mining system 
were made underground. These locations 

were marked and recorded with reference 

dosimeter numbers, as shown in Fig. 1. 

The 12 preprogrammed dosimeters were 

attached to magnetic stands then placed 

at the predetermined locations. Once all 

the dosimeters were in position and the 

researchers were positioned for the timemotion study, the testing then began.

Testing consisted of monitoring two 

complete passes (a pass consisted of the 

shearer cutting down to the tailgate and 

back) or cutting cycles of the longwall 

shearer. During a complete pass, the shearer 

traveled a distance of 615 m (2,000 ft) in 

80 minutes, which correlates to an average cutting speed of about 7.7 m (25 ft) 

per minute. The cutting speed was less 

than 7.7 m (25 ft) per minute during cutout and sump-in at the head and tail, and 

greater when traversing the remainder of 

the longwall face. After 4 hours, the dosimeters were removed from the longwall 

stageloader mining system and taken back 

to the lab for analysis. Each dosimeter 

was downloaded and saved as an Excel 

file. After all of the results were tabulated 

into an Excel spreadsheet and analyzed, 

relationships derived from the data were 

determined. A graph was generated for 

each test point plotting the equivalent 

sound level versus time. Finally, the time 

motion results were overlaid on each of the 

graphs. From these graphs, the maximum 

sound level for each location could be 

determined and related to the operation 

of the longwall mining system.

Results

To analyze the complex longwall mining 

system, the head gate and stageloader 

were divided into six measurement segments: the shearer, stageloader head gate, 

swivel pans/crusher, trough pan assembly 

(stageloader body), stageloader operator 

position and discharge/ tailpiece controls. 

The data were then organized so that the 

sound levels in each segment could be 

examined as a function of time. Operational events that were noted during the 

time-motion study were analyzed on the 

same time scale as the stationary noise measurement instruments. Thus, insight was gained about the sound field as the 

longwall system operated. 

Shearer measurement segment. Figure 2 depicts sound-level 

measurements for the shearer measurement area segment, 

Locations 1 and 2, which represents the shearer as it travels to 

the head gate, cuts out and sumps into the face and cuts back 

to the tailgate. Both locations have similar sound levels when 

the shearer is at the head gate area (dash-dot line), indicating 

that the shearer is the dominant noise source. The sound levels at Location 1 drop by 8 dB, 10 minutes after the shearer 

leaves the head gate area, at which time only the sound levels 

generated by the AFC are present. However, the sound levels at 

Location 2 stay consistently higher than at Location 1, except 

when the shearer is at the head gate. This indicates that Location 2 receives additional noise from the conveyor/head drive 

area section, which is the major noise contributor at Location 

2 when the shearer is operating at a distance down the face 

from the head gate.

Stageloader head gate segment. Sound-level results for measurement Locations 3 and 4, which represent the stageloader 

head gate area, are shown in Fig. 3. This segment is where 

the AFC ends and the stageloader AC begins. The startup 

noise from the face AFC (head drive) and shearer can be seen 

at 9:32 AM in this graph and continues until 9:45 AM as the 

shearer cuts into the head gate. The startup noise diminishes 

Figure 2 — Sound-level measurements at shearer measurement segment, 

Locations 1 and 2

Figure 3 — Sound-level measurements at stageloader head gate segment, 

Locations 3 and 4.
as the conveyors fill and the machine “sumps in.” High peaks 

occur at 9:48 AM, 10:51 AM, and 12:05 PM, when the shields 

push the stageloader forward. Other peaks at 10:45 AM and 

11:59 AM correspond to the shearer cutting at the head gate. 

In general, the dominant noise sources in this case are when 

the shearer is at the head gate, when the stageloader is moved 

and finally, from the AFC head drive and the noise from both 

conveyors, after the shearer leaves this area. 

Swivel pans/crusher segment. Figure 4 shows sound level 

results for Locations 5 and 6, which represent the area in front 

of (swivel pans) and on top of the crusher, respectively. The 

results show sound levels primarily ranging 

from 95 to 105 dB(A). Initially, when the 

conveyors went from empty to half-full to 

full, a corresponding rise in the sound levels 

was observed. However, as time went on, 

no correlation between increases in sound 

level and conveyor status (empty, half-full 

or full) could be determined. Furthermore, 

shearer location had little impact on noise 

levels observed at these measurement positions due to the distance from the shearer. 

In general, at these locations, the crushing 

and transport of material, along with the 

machinery noise, cause the dominant noise 

sources.

Trough pan assembly (stageloader body) 

segment. Figure 5 shows sound level results for Locations 7 and 8, which represent 

the area on the body of the stageloader at 

the trough pan assembly and nearby the 

stageloader body. The sudden increases 

at each location, occurring from 10:25 

AM to 10:45 AM, cannot be explained 

by the time-motion observations. Further 

investigations are needed to determine the 

cause of this event. The approximate 4 to 

5 dB difference in sound level between 

Locations 7 and 8 can be attributed to 

Location 7 being on the stageloader body 

and closer to the noise radiating from the 

enclosed body. At these locations, the 

crushing and transport of material, along 

with the machinery noise, cause the dominant noise sources.

Stageloader operator position segment.

Figure 6 shows sound level results for 

measurement Locations 9 and 10, which 

represent the area at the stageloader 

operator’s position. As Figure 6 shows, 

the stageloader operator spent about 50% 

of his time in this area (shaded area). 

Similar to what occurred at Locations 7 

and 8, the sudden sound level increase at 

Location 9 from 10:25 AM to 10:45 AM 

cannot be explained by the time-motion 

observations. The total MSHA-defined 

dose during the total observational period 

at Location 10, taken directly from the 

dosimeter, was determined to be 28% with 

a time-weighted average (TWA(8)) of 81 

dB(A). The dominant noise source in this 

area is caused by the transport of material radiating from the 

stageloader body.

Discharge/tailpiece controls segment. Sound level results for 

measurement Locations 11 and 12 are displayed in Fig. 7, and 

represent the area at the discharge segment of the stageloader. 

The controls for the crawler-mounted tailpiece are also located 

in this area. The dosimeter and magnetic stand at Location 11 

fell off of the stageloader at 9:52 AM and were placed back 

into position at 10:04 AM. This measurement segment had 

the highest sound levels of all measurement locations along 

the stageloader, ranging from 105 to 111 dB(A). Although the 

Figure 4 — Sound-level measurements at swivel pans/crusher segment, Locations 5 and 6.

Figure 5 — Sound-level measurements at trough pan assembly segment, Locations 7 and 8.
operator did not spend a majority of his 

time in this area (shaded area), exposure 

levels would likely exceed the PEL in less 

than one hour at these sound levels using 

the MSHA Reference Duration Table 

62-1. Using the MSHA criteria, the total 

accumulated dose during the cutting cycle 

between 10:46 AM and 12:10 PM at Location 12 is 1,195%, and the TWA(8) is 108 

dB(A) for this cutting cycle. In general, 

the dominant noise was caused by the 

crusher noise and the stageloader AC noise 

traveling down the enclosed stageloader 

body, acting as a wave-guide and making 

it louder at the discharge. External to the 

discharge noise source are the tailpiece 

motor and gear box contributions.

Segment comparison analysis. Analysis 

of data from a cutting cycle between 10:46 

AM and 12:10 PM is shown in Table 1. 

The results compare all the measurement 

locations by the MSHA dose, TWA(8), 

and overall equivalent sound level. The 

information presented in Table 1 is based 

strictly on the 1-hour 24-minute time 

period (cutting cycle), extrapolated to 8 

hours, and assumes that the cutting cycle 

and associated sound levels repeat exactly 

the same for an 8-hr. period. When the 

shearer is at the head gate, sound levels 

peak above 105 dB(A) (Fig. 2); however, 

these peaks have a minimal effect on the 

calculated dose because of their short 

duration. It is not until the crusher segment area that the high dose levels and 

corresponding high dB(A) TWA(8) occur. 

The 14-dB difference between Locations 

7 and 8 can be attributed to Location 7 

being on the stageloader body and closer 

to the noise radiating from the enclosed 

body. The stageloader operator position, 

at the midpoint of the stageloader body, 

is a relatively quiet area for the operator. 

Thus, the operator should be encouraged to 

be in this area whenever other work tasks 

are completed to reduce the overexposure 

to noise.

Unlike any other location along the 

stageloader, the discharge and the area 

around the tailpiece controls have excessively high sound levels during this cutting cycle, resulting in potentially high 

doses for workers located near this area during this cutting 

cycle. This noise at the discharge is mostly caused by the 

crusher noise and the stageloader AC noise traveling down 

the enclosed stageloader body, acting as a wave-guide and 

making it louder at the discharge, along with the tailpiece 

motor and gear box. 

Summary

This paper presents suggested methods for repeatable measurements of noise levels of a longwall mining system for 

prenoise and postnoise control evaluations. In addition, the 

report documents research by NIOSH on a longwall mining 

system representative of industry usage. The study involved 

monitoring the head gate area and stageloader using stationary 

time-synchronized dosimeters set up to record sound levels. 

The synchronized dosimeters allowed for sound levels, dose 

and TWA(8) comparisons along the entire stageloader from 

each measurement location. A time-motion study of the shearer 

position, stageloader movement, stageloader operator position 

and amount of material on the conveyor was conducted to 

correlate operational events on the longwall mining system 

with periods of high noise generation. The shearer’s position 

had minimal effect on the overall sound levels, as did the 

stageloader movement. The estimated MSHA 8-hr dose listed 

Figure 6 — Sound-level measurements at stageloader operator position segment, Locations 9 and 10.

Figure 7 — Sound level measurements at discharge/ tailpiece controls segment, 

Locations 11 and 12.
in Table 1 indicates that the stageloader operator is not likely 

to be overexposed at the operator position, but when at the 

tailpiece controls the potential for overexposure is excessively 

high. Initially, when the stageloader AC went from empty to 

half-full to full, a corresponding rise in the sound levels was 

observed. However, as time went on, no correlation between 

increases in sound level and conveyor status (empty, half-full 

or full) could be determined.

Identifying noise sources is the first step toward developing 

engineering noise controls to reduce longwall mining system 

worker noise overexposure. In this study, the highest equivalent 

sound levels recorded are at the stageloader discharge segment 

and tailpiece controls; these remained at about the same level 

throughout the test. The next step in reducing overexposure is 

to identify the sources causing the noise at the discharge end of 

the stageloader, because during the cutting cycle it produced 

the highest calculated TWA of 109 dB(A). The noise at the 

discharge was caused by the crusher noise and the stageloader 

AC noise traveling down the enclosed stageloader body, acting as a wave-guide and making it louder at the discharge, 

along with the tailpiece motor and gear box. Because the 

discharge area has proven to have the highest sound levels, 

future engineering noise-control research by NIOSH will be 

concentrated in this area. 

Disclaimer

The findings and conclusions in this report have not been formally disseminated by the National Institute for Occupational 

Safety and Health and should not be construed to represent 

any agency determination or policy.

References

Bauer, E.R., Podobinski, D.J., and Reeves, E.R., 2001, ��“Noise e�posure in longwal

mining and engineering controls research,” in Proceedings of Longwall USA 

International Exhibition & Conference, Intertec Publishing Corp., Overland 

Park, Kansas, pp. 51-69.

Bauer, E.R., Reeves, E.R., Durr, T.M., Zuchelli, D.R., and Armour, D., 2005, �“Testing

and evaluation of an engineering noise control on a longwall stageloader,” 

Preprint 05-58, presented at the SME Annual Meeting, Feb. 28-March 2, 

2005, Salt Lake City, Utah, Society for Mining, Metallurgy, and Exploration,

Inc., Littleton, Colorado.

Coal Age, 2006, “U.S. Longwall Census 2006 — Coal Companies Invest in

More Longwall Capacity,” S. Fiscor, Editor-in-Chief. Vol. 111, No. 2, February, pp. 26-30

Code of Federal Regulations, 1999, 64 Fed. Reg. 49548, “Health Standards for

Occupational Noise Exposure; Final Rule,” 30 CFR, Parts 56, 57, et a

Gigliotti, S.J., Davis, C.A., Niewiadomski, G., Tisdale, J.E., and Turcic, P.M., 1991,

“Review of longwall mining in the United States relative to health and safety,”

in Proceedings of the Longwall USA International Exhibition & Conference, 

Intertec Publishing Corp., Overland Park, Kansas, pp. 51-69.

NIOSH, 1999, “Fact Sheet: Work-Related Hearing Loss,” U.S. Department o

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

Control and Prevention, National Institute for Occupational Safety and

Health, Washington, DC.

Shearer measurement area 1 9 73 84 

 2 10 74 89 

Head gate 3 24 80 88 

 4 6 70 88 

Crusher 5 361 99 99 

 6 308 97 97 

Trough pan assembly 7 187 94 94 

 8 26 80 87 

Operator position 9 15 76 88 

 10 35 82 90 

Discharge and tailpiece controls 11 1,358 109 108 

 12 1,195 108 107

 MSHA-defined MSHA-defined Overall test

 Measurement dose, TWA(8), Leq,

Segment area location % dB(A) dB(A)

Table 1 — Measurement results from cutting cycle between 10:46 AM and 12:10 PM.