MIL-STD-398A
METHOD 102
IMPULSE NOISE LEVEL MEASUREMENT
1. PURPOSE. Impulse noise level measurement is conducted to insure that personnel are not exposed to a sound pressure level greater than 140 decibels during operations requiring the intentional detonation of ammunition item(s) with an operational shield.
2. DESCRIPTION OF TEST. A maximum credible incident is created with the operational shield. Sound level meters are used to measure sound pressure levels.
3. CRITERIA FOR PASSING TEST. The operational shield shall be considered
acceptable if it can be determined from noise level readings that personnel will not be exposed to overpressures greater than 140 decibels.
4. INSTRUMENTATION. All instrumentation shall meet requirements of
MIL-STD-1474.
5. TEST PROCEDURE
5.1 Location of microphones.
5.1.1 When the shield is tested in a simulated operational bay environment, noise level readings shall be taken at the following locations:
a. At the center of probable head locations of each operator. For standing locations the microphones shall be positioned 65 inches (1.65 meters) above the floor; for sitting locations it shall be 31.5 inches (0.80 meters) above the seat.
b. At representative positions where transient personnel may be located.3
5.2 Test procedure.
5.2.1 All instrumentation shall be within calibration at time of test.
5.2.2 If the shield is designed for use with more than one model or type of ammunition, select the item for maximum noise level.
5.2.3 Apply an overload equal to 25 percent or more of the filler weight of the ammunition selected for the test, unless otherwise directed in an approved test plan.
3 Microphone locations shall be as designated by the design activity in the test plan and approved by authorized authority.
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