West Virginia University
College of Engineering and Mineral Resources
WVU Noise Research‐2009
NIOSH funded study (1 R01 OH008723)
Real Time Hearing Protector Insertion Loss
Steven E. Guffey, PhD, CIH
Principal Investigator
Professor and IH Program Coordinator
Studies in Progress
1) Effects of clamp force on the effectiveness of cap‐mount ear muffs: John Lewin, MS student
2) Fit‐test results for ear muffs currently used by selected coal miners: Alexa Quinn, MS student
3) Comparison of several fit‐testing protocols to actual effectiveness for coal miners in mines. Mingyu Wu, PhD student
4) A flashing‐light intervention to improve use of HPD: John Frazer, PhD student
5) Exposure feedback as a means to improve NR during work: Brandon Takacs, PhD student & clinical faculty, WVU Ext. Service
2
Method: (MIRE)
• Microphone on shoulder
• Earplugs: pass tubes or microphones all the way through. • Muffs: microphone inside. • NR = SPLshoulder ‐ NRear
3
Custom Written Labview Data Acquisition Software
Fit Tests
• Apparatus
– National Instrument analyzer
– Larson‐Davis dosimeters
– Noise Source: speaker, amplifier, equalizer
• Variables
Subjects
Analyzer vs dosimeters
Plugs, cap‐mount muffs
Orientation to speaker
Pink noise versus simulated mine noise
Figure 1 - Spectra Types (Diffuse Field)
85
80
Sound Pressure Level (dB SPL)
–
–
–
–
–
75
Pink
Surface
Underground
Drill
70
65
60
200
250
315
400
500
630
800 1000 1250 1600 2000 2500 3150 4000 5000 6300 8000
1/3 Octave-band Frequency (Hz)
5
Fit‐Test Results, Muffs and Plugs
35.0
30.0
NR dBA
25.0
20.0
15.0
10.0
Plug
Muff
Plug Avg
5.0
0.0
0
Muff Avg
5
10
Subject
15
20
25
35
30
NR dBA
25
20
15
10
analyzer
5
dosimeter
0
analyzer Avg
dosimeter Avg
0
3
6
9
subject
12
15
18
21
6
-10
11:00:43
10:55:43
10:50:43
10:45:43
10:40:43
10:35:43
10:30:43
10:25:43
10:20:43
10:15:43
10:10:43
10:05:43
10:00:43
9:55:43
9:50:43
9:45:43
9:40:43
9:35:43
50
9:30:43
9:25:43
9:20:43
9:15:43
9:10:43
9:05:43
9:00:43
8:55:43
8:50:43
8:45:43
8:40:43
8:35:43
8:30:43
8:25:43
8:20:43
8:15:43
8:10:43
8:05:43
8:00:43
dBA
NR During Coal Mining
NR = SPLshoulder ‐ SPLear
110
100
90
80
70
60
shoulder
Roof Bolter
40
muff
30
NR
20
10
0
time
7
-20
10:14:57
10:14:18
10:13:39
10:13:00
10:12:21
10:11:42
10:11:03
10:10:24
Wearing HPD
10:09:45
10:09:06
10:08:27
10:07:48
10:07:09
10:06:30
10:05:51
10:05:12
10:04:33
10:03:54
Not wearing HPD
10:03:15
10:02:36
10:01:57
10:01:18
10:00:39
10:00:00
dBA
Prep Plant Operator
Refitting HPD
Noise Reduction
120
100
80
60
40
in ear
shoulder
NR
20
0
-40
time
* note: 3dB exchange rate, criterion 85dB
8
Preliminary Results ‐ Noise
• Ear muffs and ear plugs often have
NR < 5 dBA
• On the job NR varied greatly minute‐by‐
minute even when worn properly
• Fit‐testing of HPD:
– Invaluable in finding those with awful NR
– Highly variable: should use average of many fittings
9
Behavior Modification by Light Signaling
Light on when noise in ear (SPLear) > 80 dBA
NR = SPLshoulder ‐ SPLear
10
All Subjects
11
Removal/Reinsertion of Plug
12
Preliminary Results –Light
• Light intervention moderately effective for those who needed reminding
– No value if plugs didn’t work (worker constantly struggled for good fit)
– No value if already good compliance
Subject MeanOFF MedianOFF 75%OFF
1
2
3
4
5
6
7
8
9
11
12
20
‐2
9
0
16
19
0
8
18
0
‐1
22
‐2
9
2
18
18
‐1
5
22
0
‐2
20
‐2
9
0
16
19
0
7
19
0
‐2
90%OFF
28
4
13
9
26
26
10
21
28
1
7
StdDevOFF MeanOn
9
5
2
8
9
5
6
8
10
1
4
19
4
9
5
20
18
1
16
24
1
0
delNR
0
6
0
5
4
‐1
0
8
6
2
0
Fit
Great
Awful
Great
Awful
Great
Awful
Awful
13
Clamp Force
• Clamp force varies based on head size
• Width / breadth & length correlated with force
• 95th percentile, facial dimensions for male and female
• Especially an issue with Cap Mount Muffs
14
Other Cool Research
15