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Exposure of Law Enforcement Officers to Gunfire Noise. Chucri A. Kardous, M.S., P.E. William J. Murphy, Ph.D. U.S. Department of Health and Human Services Centers for Disease Control and Prevention National Institute for Occupational Safety and Health Cincinnati, Ohio. - PowerPoint PPT Presentation
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Chucri A. Kardous, M.S., P.E.William J. Murphy, Ph.D.
U.S. Department of Health and Human ServicesCenters for Disease Control and Prevention
National Institute for Occupational Safety and HealthCincinnati, Ohio
Exposure of Law Enforcement Officers to Gunfire Noise
Disclaimer: The findings and conclusions in this report are those of the author and do not necessarily represent the views of the National Institute for Occupational Safety and Health
Genesis of a ProblemFederal, State, and Local law-enforcement
agencies requested health hazard evaluations at indoor and outdoor firing ranges to
1. Noise exposures to weapons,
2. Control of weapons’ noise,
3. Hearing damage risk criteria,
4. Adequacy of hearing protection,
5. Lead exposure,
6. Adequacy of ventilation.
Early Challenges Equipment Limitations
Dosimeters, Microphones, Test Fixtures
Measurement Characterization of Impulses
Peak Level, Total Energy, Duration, Number
Contribution of Secondary Sources
Effect of Hearing Protection
Risk Assessment Metrics
MIL-STD 1474D, LAeq8, Auditory Hazard Units
Dosimeters and Sound Level Meters Dosimeters have a maximum response, ~ 145 dB Peak response may be clipped or reduced by
inadequate sampling rate
Typical Sound Level Meters have limited response. Some SLMs record waveforms, most do not. Relevant exposure metrics are not always
provided.
Sample Dosimeter Record
Acoustic Test Fixtures Acoustic Isolation
Dynamic Range
Maximum Level
Ear Canal Length
Flesh Simulation
Anthropometric Shape
Temperature Effects
Impulse Characterization Impulses are characterized be the Peak
level, A-duration, Reverberant decay, Spectrum and Energy.
Peak pressure level
Time durations A-duration is the elapsed time of the first
shockwave .
B-duration is the time for the decay of the peak pressure and reflections to 20 dB below the peak.
B-duration: Different Ranges
Altoona, PA Ft. Collins, CO
Spectral Content
One-third Octave Spectrum (Hz)
31 63 125 250 500 1000 2000 4000 8000
Spe
ctru
m L
evel
(dB
)
80
90
100
110
120
130ShotgunPistol
Contribution of Secondary Sources
Spherical Spreading
Multiple ReflectionsAir Absorption
Contribution of Secondary Sources
Hearing protection
Effectiveness of Level-limiting Earmuffs
Damage Risk Criteria CHABA/Coles
MIL-STD 1474D
Pfander/ Smoorenburg
A-weighted Equivalent Energy
Auditory Hazard Assessment Algorithm for Human
Current Criteria No Unprotected exposures above 140 dB peak
MIL STD 1474D below 177 for single protection.
Measure Peak, B-Duration and Number of Impulses
No Spectral Differentiation
LAeq8 less than 85 dBA.
Measure Waveform, Integrate to estimate LAeq8
Exposure is A-weighted to mimic Middle Ear
AHAAH waveform evaluations less than 500 ARUs.
Measure waveform and process with AHAAH model
Nonlinear annular ligament & Acoustic reflex
NIOSH Analyses Evaluated Human Blast Overpressure Study
LAeq8 performed the best
Evaluated Chinchilla Blast Overpressure Data
LAeq8 performed the best for temporary threshold shift data.
AHAAH performed the best for permanent threshold shift data.
Both Reports will be available soon on the NIOSH survey Reports pages.
www.cdc.gov/niosh/surveyreports
Firing Range Alert published in 2009
Conclusions New instrumentation are needed to
accurately measure and assess impulse noise exposure, including under hearing protection devices.
Standardized test methods to measure impulse noise.
New guidelines and agreed-upon damage risk criteria.
Contact information
Chuck Kardous
National Institute for Occupational Safety and Health4676 Columbia Parkway, C27
Cincinnati, Ohio 45226513-533-8146
