MIL-PRF-26542F
3.5.29 Boom operating force (see 4.5.27). The microphone boom shall provide firm positioning of the
microphone element and shall not require undue exertion for adjustment and shall prevent inadvertent
slippage of the adjusted position, during use.
3.5.30 Detrimental effect of storage. Parts accepted by the government are transported to and stored
for indefinite periods of time in depot locations having a wide range of temperature extremes. Product
shall be constructed so as to withstand the effects of government storage, such as cold- and hot-
temperature storage and standard commercial transport, such that there is no more than 1 dB of
deviation from the specified performance range after having been exposed to such storage.
3.6 Marking. Microphones shall be marked for identification in accordance with MIL-STD-1285, as
specified (see 3.1).
3.7 Workmanship. The microphone shall be processed in such a manner as to comply with the
following. After fabrication, parts and assembled equipment shall be cleaned of smudges; loose, splatter,
or excess solder; weld material; metal chips and mold release agents; or any other foreign material which
might detract from the intended operation, function, or appearance of the equipment. Screws, nuts and
bolts shall show no evidence of cross threading, mutilation, or detrimental or hazardous burrs and shall
be firmly secured. Bearing assemblies shall be free of rust, discoloration, and imperfections of ground,
honed, or lapped surfaces. Contacting surfaces shall be free of tool marks, gouge marks, nicks, or other
surface-type defects. There shall be no detrimental interference, binding, or galling. Wires and cables
shall be positioned or protected to avoid contact with rough or irregular surfaces and sharp edges, to
avoid damage to conductors or adjacent parts. Shielding on wires and cables shall be secured in a
manner that will prevent it from contacting or shorting exposed current-carrying parts. The ends of the
shielding or braid shall be secured to prevent fraying.
4. VERIFICATION
4.1 Classification of inspections. The inspections specified herein are classified as follows:
a. Qualification inspection (see 4.3).
b. Conformance inspection (see 4.4).
4.2 Inspection conditions. Unless otherwise specified, microphones shall be tested under the following
conditions: Temperature: Room ambient, +15 degrees C (+59 degrees F) to +35 degrees C (+95
degrees F); Pressure: Normal atmospheric; Humidity: Room ambient up to 90 percent relative humidity.
Magnetic field measurements shall be made in a location substantially free from stray magnetic
disturbances. No mechanical vibrations can be present. All measurements shall be made at such a
sound pressure level that the harmonic distortion of the noise produced in the test microphone by the air
pumped through the orifice of the artificial voice at low frequencies shall be sufficiently small so as not to
introduce a significant measurement error. All acoustical measurements shall be made relative to 20
µPa. All acoustical testing shall be made in a free field environment.
4.3 Qualification inspection. Qualification inspection shall be performed at a laboratory acceptable to
the Government (see 6.3), on sample units produced with equipment and procedures normally used in
production.
4.3.1 Sample size. Six (6) microphones shall be subjected to qualification inspection. If Group IV or
Group V tests are specified, 3 (three) additional units shall be required for each of these tests.
4.3.2 Inspection routine. The sample shall be subjected to the inspections specified in table I, in the
order shown, unless otherwise specified (see 3.1). All sample units shall be subjected to the inspections
of group I. The sample shall then be divided equally into 2 (two) groups; 1 (one) shall be subjected to the
group II inspections, and the other shall be subjected to group III inspections. If Group IV or Group V
tests are specified, 3 (three) additional units shall be necessary for each test.
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