Relative hazard of weapons impulses

Area of Science:

• Acoustics
• Auditory Science
• Occupational Health

Background:

• Current damage-risk criteria (DRCs) for intense noise may not accurately assess risks from impulse noise sources with differing spectral characteristics.
• Previous theoretical work suggests a spectrally dependent damage-risk criterion (DRC) for intense noise.

Purpose of the Study:

• To test a theoretically based damage-risk criterion (DRC) prediction that rifle impulses are less hazardous than cannon impulses.
• To compare the hazardous potential of rifle and cannon impulses on hearing sensitivity.
• To evaluate the implications for existing DRCs and future noise risk assessment.

Main Methods:

• Electrophysiological measures of auditory sensitivity were used in 38 cats exposed to rifle or cannon impulses.
• Animals were exposed to 60 impulses at various peak pressures, with hearing changes monitored for 2 months.
• Impulses were delivered approximately 3 seconds apart.

Main Results:

• Permanent threshold shifts began at approximately 140 dB peak pressure for rifle impulses.
• Permanent threshold shifts began at approximately 150-155 dB peak pressure for cannon impulses.
• These results confirmed the prediction that rifle impulses are less hazardous than cannon impulses at lower peak pressures.

Conclusions:

• The findings support a spectrally dependent critical level for the ear at high intensities.
• Existing DRCs may overestimate the risk from rifle impulses compared to cannon impulses.
• A revised, spectrally sensitive DRC is needed for accurate noise risk assessment.