MIL-PRF-87819B
4.7.4 Speech intelligibility (see 3.5.3). The intelligibility test shall be performed using the modified
rhyme test under the guidance of the ANSI S3.2. An AIC-25 Intercommunication System, or equivalent,
as approved by the qualifying activity, shall be used for this test. Both the talker and the listener are to be
in a pink noise environment, with the overall sound pressure levels as specified in table II. Minimum
performance levels (in percent correct), as a function of sound pressure level, shall be checked for
compliance.
4.7.5 Headset system sensitivity (see 3.5.4). The sensitivity of the device under test shall be
measured in accordance with ANSI S3.7. The headset shall be placed on a Type-1 earphone coupler
with a brass flat plate. The recommended test fixture is B&K 4152 Artificial Ear, and a DB 0909 coupler
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with a brass flat plate that is flush with the top of the coupler and maintains the 6.0 cm volume of the
coupler. The input voltage at the specified frequencies in table II shall be 1 Volt rms. The acoustic output
of the headset on the artificial ear, with a 1 kilogram weight, shall be as specified in table II.
4.7.6 Shock (drop) (see 3.5.5). The assembly shall be dropped at least six times from a height of six
feet on a concrete floor, when specified (see 3.1). The assembly shall strike at least once on the
microphone protective shield, microphone boom assembly and once on each earcup. Following the test,
the assembly shall be examined for damage to the product due to breaking or cracking and the product
shall be subjected to the acoustic quality test, as specified in 4.7.2.
4.7.7 Fungus (see 3.5.6). At the option of the contractor, the contractor shall certify that the materials
are fungus resistant materials, or test method 508 of MIL-STD-810 shall be performed. Upon completion,
the unit shall be examined for compliance.
4.7.8 Vibration (see 3.5.7). The headset-microphone shall be tested in accordance with test method
201 of MIL-STD-202. Upon completion of the test, the acoustic quality test as specified in 4.7.2 and the
visual and mechanical examination as specified in 4.7.1 shall be performed.
4.7.9 Temperature (see 3.5.8). The headset shall be tested in accordance with method 502 of
MIL-STD-810 (Low Temperature), procedures I (Storage) and II (Operation). Storage parameters shall
be 70 degrees F for 24 hours total, and Operating parameters shall be 65 degrees F constant for 2
hours. In addition, the product shall be tested against method 501 of MIL-STD-810 (High Temperature),
procedures I (Storage) and II (Operation), where the Storage parameters are + 140 degrees F for 24
hours total and the Operating parameters are + 120 degrees F Constant for 6 hours. Tests shall be
performed in sequence on the same parts, with no more than 24 hours time-lapse between the tests, a
period equivalent to that required to transport the product from one geographical climate extreme to the
other. Within 1 hour of test completion, the acoustic quality test shall be performed (see 4.7.2), as well as
the visual and mechanical examination (see 4.7.1).
4.7.10 Temperature shock (see 3.5.9). The headset shall be tested in accordance with method 503 of
MIL-STD-810 (Temperature Shock). Each of the Cold and Hot tests shall be repeated two times, for a
total of 3 (three) cycles, and then followed by mechanical and acoustic quality checks. This procedure
addresses product use in very cold climates, as well as in very hot climates. The first test shall apply
temperature extremes of 70 degrees F and then + 70 degrees F. The headset under test shall be
placed in a chamber and held at each temperature for 30 minutes, with no more than a 5 (five) minute
delay between temperature conditions to simulate the duties around a heated shack on an arctic flight
line. Within 1 hour of completing the third cycle, the visual and mechanical examination (see 4.7.1) and
the acoustic quality test shall be performed (see 4.7.2). The second test shall apply temperature
extremes of + 140 degrees F and then + 68 degrees F. The headset under test shall be placed in a
chamber and held at each temperature for 30 minutes, with no more than a 5 (five) minute delay between
temperature conditions to simulate the duties around a cooled shack on a tropical flight line. Within 1
hour of completing the third cycle, the visual and mechanical examination (see 4.7.1) and the acoustic
quality test shall be performed (see 4.7.2). See figure 3.
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