Firing Weapons from Enclosures: Predicting the Waveform

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Firing Weapons from Enclosures Predicting the
Waveform
Human Research and Engineering Directorate
Dr. Joel T. Kalb jkalb_at_arl.army.mil (410)
278-5977
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Need for Calculation Procedure
Human Research and Engineering Directorate

• In combat it is certain that weapons will be
  fired from within rooms, bunkers and alleys.
• Firer will be exposed to intense acoustic impulse
  that lasts much longer than firing in open
  position.
• Even with hearing protection, human exposure is a
  limiting factor in weapon design and use.
• There are currently no methods to predict
  pressure waveforms for different room sizes and
  weapon positions.
• Prediction will help select hearing protection
  which maximizes speech intelligibility and
  auditory situation awareness.

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Assumptions of Calculation Procedure
Human Research and Engineering Directorate

• Air-blast model begins with static explosive
  charge located behind weapon (Goodman 1960)
• Apply cardiod directivity pattern from moving
  charge model (Armendt 1956, Fansler 1995 )
• Adjust to fit outdoor arrival time, peak pressure
  and A-duration on four radials at 60 feet (Engle
  1994)
• Room reflection model traces rays from multiple
  images of weapon (Allen 1979)
• Lossless plane-wave reflection from walls, door
  and window

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Geometry for outdoor recordings, source location
and directivity pattern
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Blue gunner head Red 180Green 150
Magenta 120 Cyan 90
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Gunner waveform comparison for weapon fired
outdoors (red) and from room (blue)
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Coordinate system and location of walls, window,
door, weapon and gunner (receiver)
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Ground level grid of rooms containing real and
image weapons, room indices and rays from three
sources to receiver
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