comparison of damage risk criteria using the albuquerque blast overpressure walkup study data...
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Comparison of Damage Risk Criteria Using the Albuquerque Blast
Overpressure Walkup Study Data
Comparison of Damage Risk Criteria Using the Albuquerque Blast
Overpressure Walkup Study Data William J. Murphy
Amir Khan
Peter B. ShawHearing Loss Prevention Section
Division of Applied Research and Technology
National Institute for Occupational Safety and Health
William J. Murphy
Amir Khan
Peter B. ShawHearing Loss Prevention Section
Division of Applied Research and Technology
National Institute for Occupational Safety and Health
The results reported in this paper represent the opinions of the authors and are not representative of the policies of the
National Institute for Occupational Safety and Health.
The results reported in this paper represent the opinions of the authors and are not representative of the policies of the
National Institute for Occupational Safety and Health.
Blast Overpressure StudiesBlast Overpressure Studies
OutlineOutline Blast Overpressure Exposure Evaluations
MilStd 1474D
LAeq8hr Protected & Unprotected
AHAAH Warned & Unwarned
Statistical model for effects threshold
Population Averaged Model Audiometric Failures
Audiometric and Conditional Failures
Dose Response Curves
Blast Overpressure Exposure Evaluations
MilStd 1474D
LAeq8hr Protected & Unprotected
AHAAH Warned & Unwarned
Statistical model for effects threshold
Population Averaged Model Audiometric Failures
Audiometric and Conditional Failures
Dose Response Curves
Outline continuedOutline continued Exposure Assessment Comparisons
Threshold Estimates from BOP Study
Fitting Performance
Damage Risk Criteria Implications
MilStd 1474D: 177 dB Limit
LAeq8hr: 85 dBA Limit
AHAAH: 500 Auditory Hazard Unit (AHU) limit
Exposure Assessment Comparisons
Threshold Estimates from BOP Study
Fitting Performance
Damage Risk Criteria Implications
MilStd 1474D: 177 dB Limit
LAeq8hr: 85 dBA Limit
AHAAH: 500 Auditory Hazard Unit (AHU) limit
MilStd 1474D Free-Field Exposure
MilStd 1474D Free-Field Exposure
170
175
180
185
190
195
200
170175
180185
190
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
6
Mil-
Std
147
4D (
dB)
Peak Exposure Level (dB)
Num
ber o
f Sho
ts
Mil-Std 1474D5 meter BOP Study 174
176 178 180 182 184 186 177 dB Threshold Limit
170
175
180
185
190
195
200
170175
180185
190
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
Mil-
Std
147
4D
(d
B)
Peak Exposure Level (dB)
Num
ber o
f Sho
ts
Mil-Std 1474D5 meter BOP Study
Modified muff 174 176 178 180 190 195 200 177 dB Threshold Limit
170
175
180
185
190
195
200
170175
180185
190
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
Mil-
Std
14
74D
(dB
)
Peak Exposure Level (dB)
Num
ber o
f Sho
ts
Mil-Std 1474D1 meter BOP Study
Modified muff
170 175 180 185 190 190 195 177 dB Threshold Limit
170
175
180
185
190
195
200
170175
180185
190
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
Mil-
Std
147
4D
(d
B)
Peak Exposure Level (dB)
Num
ber o
f Sho
ts
Mil-Std 1474D3 meter BOP Study
Modified muff 175.5 176.0 176.5 177.0 177.5 178.0 180 177 dB Threshold Limit
75
80
85
90
95
100
105
110
115
12
34
567
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
8 ho
ur E
quiv
alen
t Le
vel (
dBA
)
Exposure Level
Num
ber o
f Sho
ts
LAeq8hr with 85 dB Threshold1m BOP studyModified muff
90 95 100 105 110 100 105 110 115 85 dBA Threshold LimitHazardous Exposure
75
80
85
90
95
100
105
110
115
12
34
567
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
8 h
our
Equ
ival
ent
Lev
el (
dB
A)
Exposure Level
Num
ber o
f Sho
ts
LAeq8hr with 85 dB Threshold3 meter BOP Study
Modified muff
103.5 104.0 104.5 105.0 95 100 105 110 115 85 dBA Threshold LimitHazardous Exposure
75
80
85
90
95
100
105
110
115
12
34
567
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
8 h
our
Equ
ival
ent
Lev
el (
dB
A)
Exposure Level
Num
ber o
f Sho
ts
LAeq8hr with 85 dB Threshold5 meter BOP Study
Modified muff
90 95 100 105 95 100 105 110 115 85 dBA Threshold LimitSafe ExposureHazardous Exposure
0
2000
4000
6000
8000
170175180185190612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
Aud
itory
Haz
ard
Uni
ts (
AH
U)
Peak Exposure Level (dB)N
umbe
r of
Sho
ts
Warned AHAAH Analysis1 meter BOP study
Modified muff0 2000 4000 6000 8000 500 AHU Threshold LimitSafe ExposureHazardous Exposure
0
2000
4000
6000
8000
170175
180185
190
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
Aud
itory
Haz
ard
Uni
ts (
AH
U)
Peak Exposure Level (dB)
Num
ber o
f Sho
ts
Warned AHAAH Analysis3 meter BOP study
Modified muff
0 1000 2000 30004000 500 AHU Threshold LimitSafe ExposureHazardous Exposure
0
2000
4000
6000
8000
170175
180185
190
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
Aud
itory
Haz
ard
Uni
ts (
AH
U)
Peak Exposure Level (dB)
Num
ber o
f Sho
ts
Warned AHAAH Analysis5 meter BOP study
Modified muff
0 1000 2000 3000 4000 AHAAH 500 ARU ThresholdSafe ExposureHazardous Exposure
Statistical Analysis of BOP DataStatistical Analysis of BOP Data
Obtained the waveforms from Data Archive from USAARL-MRMC and USARL – HRED MILSTD 1474D – B duration (also computed A & C
durations) LAeq8hr – Protected and Unprotected AHAAH model – Protected Warned and Unwarned
Checked against Chan et al. 2001, Ahroon & Patterson 2005, Price (2005), Jokel (2007)
Obtained the injury data from USAARL-MRMC Checked the injury data against 1999 Contractor
report DAMD17-96-6007
Obtained the waveforms from Data Archive from USAARL-MRMC and USARL – HRED MILSTD 1474D – B duration (also computed A & C
durations) LAeq8hr – Protected and Unprotected AHAAH model – Protected Warned and Unwarned
Checked against Chan et al. 2001, Ahroon & Patterson 2005, Price (2005), Jokel (2007)
Obtained the injury data from USAARL-MRMC Checked the injury data against 1999 Contractor
report DAMD17-96-6007
Applied a General Estimating Equations to evaluate the Population Averaged effects using xtgee in Stata.
Represents the response pattern of the population as a whole
Makes no assumptions regarding propagation of failure through to other exposure levels
Tells us nothing about the chances of an individual subject failing within the exposure.
Tells us about the chance of having a failure in the population.
Applied a General Estimating Equations to evaluate the Population Averaged effects using xtgee in Stata.
Represents the response pattern of the population as a whole
Makes no assumptions regarding propagation of failure through to other exposure levels
Tells us nothing about the chances of an individual subject failing within the exposure.
Tells us about the chance of having a failure in the population.
Statistical Analysis of BOP DataStatistical Analysis of BOP Data
0 1ˆ ˆ
1ˆ
1 ijxf
e
Mil STD 1474 DMil STD 1474 D00
.05
0.2
0.4
0.6
0.8
1.0
Failu
re R
ate
150 160 170 180 190 200 210dB
95% confidence limits GEE population-average
Audiometric FailureMIL STD 1474D
00.0
50.
20.
40.
60.
81.
0Fa
ilure
Rat
e
150 160 170 180 190 200 210dB
95% confidence limits GEE population-average
Audiometric or Conditional FailureMIL STD 1474D
185 dB193 dB
LAeq8hr Unprotected LevelsLAeq8hr Unprotected Levels00
.05
0.2
0.4
0.6
0.8
1.0
Failu
re R
ate
100 105 110 115 120 125 130 135 140dB
95% confidence limits GEE population-average
Audiometric FailureLAeq_8hr: Unprotected
00.0
50.
20.
40.
60.
81.
0Fa
ilure
Rat
e
100 105 110 115 120 125 130 135 140dB
95% confidence limits GEE population-average
Audiometric or Conditional FailureLAeq_8hr: Unprotected
115 dB124 dB
LAeq8hr Protected LevelsLAeq8hr Protected Levels00
.05
0.2
0.4
0.6
0.8
1.0
Failu
re R
ate
80 85 90 95 100 105 110 115 120dB
95% confidence limits GEE population-average
Audiometric FailureLAeq_8hr: Protected
00.0
50.
20.
40.
60.
81.
0Fa
ilure
Rat
e
80 85 90 95 100 105 110 115 120dB
95% confidence limits GEE population-average
Audiometric or Conditional FailureLAeq_8hr: Protected
101 dB109 dB
AHAAH Unwarned ModelAHAAH Unwarned Model00
.05
0.2
0.4
0.6
0.8
1.0
Failu
re R
ate
0 5000 10000 15000 20000 25000 30000AHU
95% confidence limits GEE population-average
Audiometric FailureAHAAH: Unwarned
00.0
50.
20.
40.
60.
81.
0Fa
ilure
Rat
e
0 5000 10000 15000 20000 25000 30000AHU
95% confidence limits GEE population-average
Audiometric or Conditional FailureAHAAH: Unwarned
3053 AHU10109 AHU
AHAAH Warned ModelAHAAH Warned Model00
.05
0.2
0.4
0.6
0.8
1.0
Failu
re R
ate
0 1000 2000 3000 4000 5000 6000 7000 8000AHU
95% confidence limits GEE population-average
Audiometric FailureAHAAH: Warned
00.0
50.
20.
40.
60.
81.
0Fa
ilure
Rat
e
0 1000 2000 3000 4000 5000 6000 7000 8000AHU
95% confidence limits GEE population-average
Audiometric or Conditional FailureAHAAH: Warned
718 AHU2480 AHU
5% Failure Thresholds L(95,95)5% Failure Thresholds L(95,95)
Damage Risk Criterion
Audiometric Failures
Audiometric & Conditional
Failures
AHAAH Warned 2480 AHU 718 AHU
AHAAH Unwarned 10109 AHU 3053 AHU
LAeq8hr Unprotected 124 dB 115 dB
LAeq8hr Protected 109 dB 101 dB
MilStd 1474D 193 dB 185 dB
Five Exposure Assessments Compared
Five Exposure Assessments Compared
Damage Risk Criterion
Audiometric Failures
Audiometric & Conditional
Failures
LAeq8hr Unprotected 273.73 630.26
MilStd 1474 D 282.01 636.25
AHAAH Unwarned 304.51 650.85
LAeq8hr Protected 305.80 650.05
AHAAH Warned 307.13 653.99
QIC: Lower value indicates a better fitQIC = Quasi Likelihood under the independence model Information
Criterion
Mil-Std ObservationsMil-Std Observations
Mil-Std 1474D
L(95,95) with No Presumed Auditory Failures Chan : L(95,95) = 193 dB NIOSH : L(95,95) = 193 dB
Chan’s analysis: Presumed Auditory Failures Add 9 dB for threshold of L(95,95) = 186 dB
NIOSH analysis (Auditory & Conditional Failures) L(95,95) = 185 dB. Add 8 dB for Population Average threshold for
the L(95,95) lower confidence bound.
Mil-Std 1474D
L(95,95) with No Presumed Auditory Failures Chan : L(95,95) = 193 dB NIOSH : L(95,95) = 193 dB
Chan’s analysis: Presumed Auditory Failures Add 9 dB for threshold of L(95,95) = 186 dB
NIOSH analysis (Auditory & Conditional Failures) L(95,95) = 185 dB. Add 8 dB for Population Average threshold for
the L(95,95) lower confidence bound.
LAeq8hr ObservationsLAeq8hr Observations LAeq8hr Protected versus Unprotected
French Weapon Noise Criteria:
LAeq8hr < 85 dB Unprotected
Chan’s analysis without presumed failures LAeq8hr < 100 dB Protected (assumed 15 dB for protectors)
Unprotected limit 124 dB without presumed failures
NIOSH analysis without presumed failures
14 dB HPD effect for Protection
Unprotected limit: 124 dB Audiometric Failures
Unprotected limit: 115 dB Aud. & Cond. Failures
Protected limit: 101 dB Aud. & Cond. Failures
LAeq8hr Protected versus Unprotected
French Weapon Noise Criteria:
LAeq8hr < 85 dB Unprotected
Chan’s analysis without presumed failures LAeq8hr < 100 dB Protected (assumed 15 dB for protectors)
Unprotected limit 124 dB without presumed failures
NIOSH analysis without presumed failures
14 dB HPD effect for Protection
Unprotected limit: 124 dB Audiometric Failures
Unprotected limit: 115 dB Aud. & Cond. Failures
Protected limit: 101 dB Aud. & Cond. Failures
AHAAH ObservationsAHAAH Observations NIOSH Analysis L(95,95) Audiometric
failures (no presumed failures) Unwarned Threshold = 10109 AHU Warned Threshold = 2480 AHU
NIOSH Analysis L(95,95) Audiometric and Conditional Failures (no presumed failures) Unwarned Threshold = 3053 AHU Warned Threshold = 718 AHU
AHAAH Model proposes a 500 AHU Limit which is more conservative than the data suggest
NIOSH Analysis L(95,95) Audiometric failures (no presumed failures) Unwarned Threshold = 10109 AHU Warned Threshold = 2480 AHU
NIOSH Analysis L(95,95) Audiometric and Conditional Failures (no presumed failures) Unwarned Threshold = 3053 AHU Warned Threshold = 718 AHU
AHAAH Model proposes a 500 AHU Limit which is more conservative than the data suggest
Concerns for AHAAH ModelConcerns for AHAAH Model
Predictions of Hazard at Levels 3 & 4 not really tested in BOP study.
Experiments can be designed to test this.
Predictions of Hazard at Levels 3 & 4 not really tested in BOP study.
Experiments can be designed to test this.
0
2000
4000
6000
8000
170175180185190612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
Aud
itory
Haz
ard
Uni
ts (
AH
U)
Peak Exposure Level (dB)N
umbe
r of
Sho
ts
Warned AHAAH Analysis1 meter BOP study
Modified muff0 2000 4000 6000 8000 500 AHU Threshold LimitSafe ExposureHazardous Exposure
75
80
85
90
95
100
105
110
115
12
34
567
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
8 ho
ur E
quiv
alen
t Le
vel (
dBA
)
Exposure Level
Num
ber o
f Sho
ts
LAeq8hr with 85 dB Threshold1m BOP studyModified muff
90 95 100 105 110 100 105 110 115 85 dBA Threshold LimitHazardous Exposure
170
175
180
185
190
195
200
170175
180185
190
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
612
25
50
100
Mil-
Std
147
4D (
dB)
Peak Exposure Level (dB)
Num
ber o
f Sho
ts
Mil-Std 1474D1 meter BOP Study
Modified muff
170 175 180 185 190 190 195 177 dB Threshold Limit
Concerns for AHAAH ModelConcerns for AHAAH Model Justification for 500 AHU as a threshold limit
Warned limit 718 or 2480 AHU – Population Average, L(95, 95)
Unwarned Limit 3053 or 10109 AHU – Population Average, L(95,
95)
Validation of the Warned/Unwarned middle ear
No consideration given for adaptation/fatigue
Model turns Warned condition ON but not OFF
Justification for 500 AHU as a threshold limit
Warned limit 718 or 2480 AHU – Population Average, L(95, 95)
Unwarned Limit 3053 or 10109 AHU – Population Average, L(95,
95)
Validation of the Warned/Unwarned middle ear
No consideration given for adaptation/fatigue
Model turns Warned condition ON but not OFF
Questions?Questions?
William Murphy
4676 Columbia Parkway, MS C-27
Cincinnati, OH 45226-1998
513-533-8125
William Murphy
4676 Columbia Parkway, MS C-27
Cincinnati, OH 45226-1998
513-533-8125