Avoiding Noise Avoiding Noise Overexposure at Overexposure at 

Underground and Surface Underground and Surface Coal Mines, Preparation Coal Mines, Preparation 

Plants and Surface DrillingPlants and Surface Drilling

Eric R. Bauer, Ph.D., P.E.Eric R. Bauer, Ph.D., P.E.

Mining Hearing Loss Prevention WorkshopMining Hearing Loss Prevention WorkshopJune 21June 21--22, 200522, 2005

Pittsburgh Research Laboratory

OutlineOutline

•Introduction•Exposure Reduction Methods

•Exposure Reduction Planning

•Exposure Reduction Examples

•Summary

IntroductionIntroduction

• Noise-Induced Hearing Loss (NIHL) is the most common occupational illness in the United States

• Workers in mining and surface drilling can be exposed to hazardous noise levels

• Both industries have recognized the importance of controlling overexposures and have taken the initiative to prevent overexposures

Introduction (con’t)Introduction (con’t)• Cross-Sectional Survey Project has shown 

that overexposures (dose > MSHA PEL of 100%) occurred:• 43% of face workers in UG coal mines• 30% in surface coal mines (primarily dragline oiler)• 45% in coal prep plants (primarily plant controls man)

Note:  Worker doses/overexposures were measured using MSHA Permissible Exposure Level (PEL) criteria in Part 62:

•A-weighting•90 dB Threshold Level•5 dB Exchange Rate•90 dB Criterion Level•Slow Response•140 dB Upper Limit

Introduction (con’t)Introduction (con’t)

• NIOSH research of surface drilling operations has shown a significant hearing loss at the 4000 Hz frequency which indicates noise-induced hearing loss (NIHL) attributable to noise exposure during drilling operations

Exposure Reduction MethodsExposure Reduction Methods

Two exposure reduction methodsare:

• Engineering noise controls• Administrative noise controls

And...protection using HPD’s

Exposure Reduction MethodsExposure Reduction Methods

Engineering noise controls:• Reduce the sound levels of the 

equipment or process that reach the worker... 

i.e. 

“Isolate the noise from the worker”

Exposure Reduction MethodsExposure Reduction Methods

Administrative noise controls:• Limit the workers exposure to the 

noise by removing the worker from the noise source by distance, time, task efficiency, job rotation...

i.e. 

“Isolate the worker from the noise”

Exposure Reduction MethodsExposure Reduction Methods

An engineering noise control reduces the sound level that reaches the worker to 

reduce exposure

While

An administrative noise control reduces the time the worker is exposed to the sound 

level to reduce exposure

Engineering or Administrative?Engineering or Administrative?Confusing?  CERTAINLY

For instance, a quiet booth is an engineering noise control because the sound level reaching the worker is reduced by a physical barrier between worker and source

But

requiring the worker to spend time in the booth is an administrative noise control because it reduces the time of exposure to the sound level outside the booth

Engineering or Administrative?Engineering or Administrative?

The bottom line is...

If the control reduces the worker’s exposure, then what it is called is not that important.

Exposure ReductionExposure Reduction

What does and does not work when attempting to reduce exposures?

• Trial-and-error does not work but a systematic approach does

• “Same old, same old” attitude does not work but “thinking outside the box” does

• Half shift switch out does not work but selective task switching does

Exposure Reduction PlanningExposure Reduction Planning

Effective implementation of administrative noise controls requires a complete understanding of a workers noise exposure:

1. Full-shift dosimetry2. Task observations of worker3. Comparison of dose to tasks 4. Representative sound level measurements5. Selection/implementation of appropriate 

administrative noise control6. Follow-up/Modify as needed

Exposure Reduction ExamplesExposure Reduction Examples

Examples include:• Belt drive• Quiet booths• Heavy equipment operators at surface mines• Roof bolter operator using spare bolter• Mechanic working near noise source• Dragline oiler• Stageloader operator• Longwall dinner hole• Surface drilling• Job rotation

Belt Drive UndergroundBelt Drive Underground

Problem:• Belt drives, tail rollers, transfer points are 

noisy• Difficult to clean around tail roller because of 

float coal dust/rock dust build-up (1 to 2 ft)

Result:• Belt cleaners exposed to noise

Belt Drive UndergroundBelt Drive Underground

Belt Drive UndergroundBelt Drive Underground

Solution:• Limit time belt cleaner works near tail roller

How:• Dig out/back the build-up of coal dust/rock 

dust so cleaning can be done quicker and easier, thus less time/less exposure

• Complete on an off-shift or monitor worker’s dose if during production shift

Quiet Booth in Prep PlantQuiet Booth in Prep Plant

Problem:• Noisy floors• Worker required to stay on a certain floor or 

certain location

Result:• Worker overexposed to noise

Quiet Booth in Prep PlantQuiet Booth in Prep Plant

Plant worker’s dose ranged from 104 to 165%

Quiet Booth in Prep PlantQuiet Booth in Prep Plant

Plant worker’s dose ranged from 147 to 206%

Quiet Booth in Prep PlantQuiet Booth in Prep Plant

78 dB(A) Inside booth

91 to 93 dB(A) Outside booth

Quiet Booth in Prep PlantQuiet Booth in Prep Plant

Solution(s):• (First example) Complete construction of the 

quiet booth (well insulated, appropriate heat and air conditioning, remote monitoring, creature comforts) for worker to go to when not inspecting, adjusting, or cleaning equipment

• (Second example) Provide small booth simply for worker to sit in while loading house coal

Heavy Equipment OperatorsHeavy Equipment Operators

Problem:• Noisy engines and operation

Result:• Overexposure of operator

Heavy Equipment OperatorsHeavy Equipment Operators

Truck A – Outside dose: 111%Inside dose (operator): 12%

Truck B – Outside dose: 396%Inside dose (operator): 98%

Heavy Equipment OperatorsHeavy Equipment Operators

Solution(s):• Take truck out of service, operator use 

different truck• Repair noisy equipment• Provide acoustically treated cab• Instruct operator to keep doors and windows 

closed

Operating Spare BolterOperating Spare Bolter

Problem:• Noisy spare roof bolting machine on CM section

Result:• High rate of dose accumulation for roof bolting 

machine operator• For shift (including spare bolter operation): 

230% total dose in 630 min (0.37%/min)• Spare bolter operation: 145% dose in 140 min 

(1.04%/min)

1 2 3 4 5 6 7 8 9 100

50

100

150

200

250

TIME, hrs

CU

MU

LATI

VE 

DO

SE, p

erce

nt

PEL-90dB

Lunch

Bolting with spare RBM

Bolting with main RBM

Tramming RBM

High noise accumulation

Duration of exposure

Percent exposure

Operating Spare BolterOperating Spare Bolter

Solution(s):• Limit operation of spare roof bolting machine• Replace spare roof bolting machine• Fix/quiet spare roof bolting machine

Working Near Noise SourcesWorking Near Noise Sources

Problem:• Mechanic/Electrician working near auxiliary 

fans (splicing a roof bolting machine trailing cable)

Result:• Mechanic/Electrician experiencing exposure to 

high noise levels

Splicing trailing cable near auxiliary fans

0

20

40

60

80

100

120

140

160

180

0 60 120 180 240 300 360 420 480 540 600

TIME, hr

CU

MU

LATI

VE D

OSE

, per

cent

1 2 3 4 5 6 7 8 9 10

Dose: 115%

Time: 75 min

MSHA PEL 90 dBA

App. 1.5 %/min

App. O.1%/min

Working Near Noise SourcesWorking Near Noise Sources

X

Face

Cable

Working Near Noise SourcesWorking Near Noise Sources

Solution(s):• Drag trailing cable away from fans• Faster cable splicing methods• Provide a barrier/shield• Don’t work, rest, stand, converse near known 

loud noise sources• Training of workers to recognize noise sources 

and potential sources of exposure and how to avoid them

Dragline Dragline OilerOiler

Problem:• House of dragline noisy

Result:• Dragline oiler accumulating significant noise 

exposure while working in house of dragline

Marion 8750 DraglineMarion 8750 Dragline

0 1 2 3 4 5 6 7 80

50

100

150

200

TIME, hrs

CU

MU

LATI

VE D

OSE

, per

cent

In cab

Safety checks in house

Cleaning mostly in rev. frame

In cab

In house, sweeping, using comp. airIn cab

Walking

MSHA PEL 90 dBA

Dragline Dragline OilerOiler

Solution(s):• Limit dragline oilers time working in house• Switch out oiler with dragline operator or 

groundsman (dozer operator)• Perform maintenance, cleaning, etc. on off 

shifts or when dragline is down for routine maintenance or repairs

• Oiler must insert/employ hearing protection prior to entering house

LongwallLongwall StageloaderStageloader OperatorOperator

Problem:• Stageloader noisy around head drive, crusher, 

and especially tail piece

Result:• Stageloader operator accumulating significant 

noise exposure while working around stageloader, especially when near discharge

• Measured doses up to 386%

LongwallLongwall StageloaderStageloader OperatorOperator

LongwallLongwall StageloaderStageloader OperatorOperator

0

25

50

75

100

125

150

175

200

225

7:00 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00

TIME OF SHIFT, hr

CU

MU

LATI

VE D

OSE

, per

cent

MSHA PEL, 90 dBA

Belt off

Lunch in dinnerhole

Mantrip out

Mantrip in

Note: Shearer and belt off 8:10 to 11:05  am

Mostly at discharge & along belt

At controls along belt, outby discharge 

Mostly at discharge

Along belt and at discharge

LongwallLongwall StageloaderStageloader OperatorOperator

Solution(s):• Limit stageloader operator’s time working near 

discharge• Locate controls and monitors away from 

stageloader• Provide sound-proof booth for stageloader

operator

LongwallLongwall Dinner HoleDinner Hole

Problem:• Dinner hole (picnic table) located in crosscut 

adjacent to stageloader (located to remain out of airflow and close to face)

• Measured noise levels approaching 90 dB(A)

Result:• Longwall workers exposed to noise while eating 

lunch

LongwallLongwall Dinner HoleDinner Hole

LongwallLongwall Dinner HoleDinner Hole

Solution(s):• Locate dinner hole in track entry (use brattice 

cloth to block airflow)• Locate dinner hole in crosscut as far from 

stageloader as possible• Locate dinner hole where noise levels are 85 

dB(A) or less

Surface DrillingSurface Drilling

Problem:• Surface drills are noisy while drilling

Result:• Driller and helper experiencing high noise 

exposures from drilling noise

Surface DrillingSurface Drilling

Rubber Tired

Track Mounted

0

10

20

30

40

50

60

70

80

90

100

110

120

130

9:36

:58 

AM

9:44

:08 

AM

9:51

:18 

AM

9:58

:28 

AM

10:0

5:38

 AM

10:1

2:48

 AM

10:1

9:58

 AM

10:2

7:08

 AM

10:3

4:18

 AM

10:4

1:28

 AM

10:4

8:38

 AM

10:5

5:48

 AM

11:0

2:58

 AM

11:1

0:08

 AM

11:1

7:18

 AM

11:2

4:28

 AM

11:3

1:38

 AM

11:3

8:48

 AM

11:4

5:58

 AM

11:5

3:08

 AM

12:0

0:18

 PM

12:0

7:28

 PM

12:1

4:38

 PM

12:2

1:48

 PM

12:2

8:58

 PM

12:3

6:08

 PM

12:4

3:18

 PM

12:5

0:28

 PM

12:5

7:38

 PM

1:04

:48 

PM

1:11

:58 

PM

1:19

:08 

PM

1:26

:18 

PM

Surface Drilling Dosimeter DataSurface Drilling Dosimeter Data

Time (10 Seconds)  9:36AM – 12:53 PM

Decibels

(dB(A))

90 dB(A)

Rig  Shut  Down

Hammering Casing

Drilling

Flushing Hole

Surface DrillingSurface Drilling

Solution(s):• Locate helper in quiet zones• If cab is installed, instruct driller to keep 

windows and doors closed.• Relocate driller away from rig when possible• Instruct driller/helper to avoid loud noise areas 

(compressor, fan, engine, dust collector, exhaust)

Job RotationJob Rotation

Problem:• Sound levels vary depending on occupation, 

equipment operated, worker location, task, etc.

Result:• Workers experience different levels of exposure

Job RotationJob Rotation

Solution(s):• Selective rotation based on dose/observations• Switch out high exposure occupations with 

lower exposure occupations

Job RotationJob Rotation

13-192Shieldman36-386Stageloader Oper.

17-57Center Bolter Oper.9-275M/B RB Oper.

0-6314-130

Dragline Oper.Groundsman

46-318Dragline Oiler

13-192Shieldman33-266Head Shearer Oper.

33-26613-192

Head Shearer Oper.Shieldman

22-785Tail Shearer Oper.

33-1656-297

Shuttle Car Oper.Laborer/Utility

57-355RBM Oper.

25-81LM Oper.45-323M/B Oper.

33-1656-297

Shuttle Car Oper.Laborer/Utility

44-347CM Oper.

Range MSHA PEL Dose, %

OccupationRange MSHA PEL Dose, %

Occupation

Rotate ToRotate From

Notes on Exposure ReductionNotes on Exposure Reduction

First... Success of any exposure reduction is contingent on working at lower sound levels

Second... Any exposure reduction must not introduce additional health or safety hazards

SummarySummary

To avoid overexposure:• Use a systematic approach• Employ innovative solutions• Involve workers in the process• Conduct noise awareness training• Proper use of HPD’s

For more informationFor more information

Eric Bauer

NIOSH Pittsburgh Research LaboratoryNIOSH Pittsburgh Research LaboratoryPhone: 412Phone: 412--386386--6518     Fax: 4126518     Fax: 412--386386--48654865

ehb2@cdc.govehb2@cdc.govwww.cdc.gov/niosh/miningwww.cdc.gov/niosh/mining

Pittsburgh Research Laboratory