comparison of ipil measured with gunshot and shock tube noise
TRANSCRIPT
Comparison of IPIL measured with
Gunshot and Shock tube noise sources
William J. Murphy1
Elliott H. Berger2
William A. Ahroon3
1Hearing Loss Prevention Team
National Institute for Occupational Safety & Health
2Personal Safety Division
3M
3Auditory Protection and Performance Division
US Aeromedical Research Laboratories
Disclaimer: The findings and conclusions in this report are those of the authors and do not necessarily
represent the views of CDC, NIOSH, 3M, US Army or USAARL. Products referenced in the presentation
are not endorsed by US Government (CDC/NIOSH, USAARL).
Acoustical Society of America, October 28, 2014
Learning objectives
• Descriptors of impulse noise
• Characterize impulse sources
• Measurement of Impulse Peak Insertion
Loss (IPIL) ANSI S12.42-2010 method
• IPIL measurements for various HPDs
• Effect of spectrum on IPIL
• Future research
Impulse Noise Descriptors
Example Impulsive Noises
IPIL Configuration
Impulse Peak Insertion Loss Theory
L: Three impulse levels 132, 150, 168 dB
i: Five samples of each HPD condition
j: Five fittings of each HPD sample
k: 1 to 3 shots for each HPD sample fitting
Acoustic Test Fixture & HPDs
Etymōtic Research
ETYPlugs
3M™ Peltor™ TacticalPro
Communications Headset
2011 Rudyard, MI
Colt® AR-15 Rifle
0.223 Caliber
Cartridge
Peak levels
• 170, 149, 132 dB
Four HPD Conditions
Five Samples / HPD
Five Fittings / Sample
Three Shots / Fitting
Rudyard 2011 AR-15 Gunshot
Acoustic Shock Tubes
2011 Aberdeen Proving Ground,MD
Acoustic Shock Tube
and Horn
• Compressed Air
• Photographic Paper
Peak levels
• 165,150, 132 dB
Three HPD Conditions
Five Samples / HPD
Five Fittings / Sample
One Shots / Fitting
USARL 2011 Acoustic Shock Tube
2011 Fort Rucker, AL
Acoustic Shock Tube
and Horn
Mylar® Membrane
Aluminum Foil
Peak levels
• 164,148, 135 dB
Five HPD Conditions
Five Samples / HPD
Five Fittings / Sample
One Shot / Fitting
USAARL 2011 Acoustic Shock Tube
2012 & 2013 Indianapolis, IN
Acoustic shocktube
and horn
• Mylar® membrane
Peak levels
• 169, 148, 131 dB
Five HPD Conditions
Five Samples / HPD
Two Fittings / Sample
One Shot / Fitting
EARCAL Acoustic Shock Tube
Comparison of Spectra
ETYPlugs IPIL
ETYPlugs Insertion Loss
TacticalPro IPIL
TacticalPro Insertion Loss
Dual HPDs IPIL
Dual HPDs Insertion Loss
Insertion Loss Across Laboratories
• ETYPlugs IL agree well below 4000 Hz.
• TacticalPro IL varies considerably at lowest
impulse levels.
• TacticalPro IL better agreement at mid and
high impulse levels
• Insertion loss is dependent upon the high-
frequency content of source.
• Bone Conduction will be an important
factor for evaluating double protection
IPIL Across Laboratories
• IPIL is greater for the rifle which has
more high-frequency content than shock
tubes.
• IPIL for rifle were more consistent for
TacticalPro.
• IPIL for shock tube exhibit about 5-10 dB
variability.
• TacticalPro exhibits greater change in
IPIL than the ETYPlugs with level and
frequency content.
Future Research
• Develop an Impulse Noise Reduction Rating
based upon insertion loss.
• Develop a method that considers a range of
spectra for Impulse Noise Reduction Rating.
• Evaluate more nonlinear HPDs with different
sources.
• Investigate the effect of the acoustic test
fixture’s noise floor at high frequencies.
• Develop/Verify the Army’s HPD model.
Questions?
William J. Murphy, PhD
(513) 533-8125
Hearing Loss Prevention Team
Our research is sound.
3M EAR Classic IPIL
3M EAR Classic Insertion Loss Spectra