MIL-PRF-87819B
3.4.9 Headband and headband parts. The headband material shall provide sufficient pressure of the
earcups against the user's head to meet or exceed the noise-attenuation requirements of this
specification. It shall also conform to the environmental, headband flexing, and shock (drop)
requirements of this specification. It shall include an adjustment mechanism which can be used to easily
and smoothly modify and firmly set the earcup position for the typical user head size, as specified on
figure 2. The adjustment shall not loosen inadvertently during use. There shall be no protruding
hardware or excess wire, which could become entangled with other parts of the headset or other
equipment. The headband shall not separate from the earcup yoke during normal use, including the use
of quick-don oxygen mask assemblies. The use of any parts to secure the yoke to the earcup, which may
become inadvertently detached, shall not be used. This includes, but is not limited to, "c-clips" or "e-
clips". Neither the headband nor any attachments to it (pad, support, etc.) shall obstruct the normal
adjustment of the headband and earcups.
3.4.9.1 Headband pad. The headband pad shall protect the user's head from the weight of the
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headset, displacing no less than 0.165 lbs/in of force. The pad surface material shall resist puncturing,
and shall not tear, crack or otherwise degrade under the environmental conditions specified (see 3.5.5,
3.5.6, 3.5.8, 3.5.9, 3.5.10, 3.5.15). Any filler used in the pad shall not leak from the pad in the event of
puncture to the surface. The pad shall be removable during normal maintenance without damaging the
headset and shall not become inadvertently detached during use.
3.4.9.2 Headband pad support. If the headset is supplied with a support for the headband pad, it shall
provide a firm foundation for the headband pad across the pad's full dimensions. It shall be firmly
attached and shall not become inadvertently detached from the headband during normal use.
3.4.10 Connectors. The connectors to be used shall be PIN U-174/U as specified in MIL-DTL-9177/2,
for interface to the console, and PIN U-173/U as specified in Air Force drawing 57B12662, for interface to
the emergency oxygen mask. Electrically and mechanically compatible connectors may be used, if they
meet or exceed the performance requirements specified. All other connectors used shall be as specified
(see 3.1).
3.5 Performance characteristics.
3.5.1 Acoustic quality (see 4.7.2). There shall be no buzzing, rattles, or other spurious noises, which
would impair the quality of the reproduced signal.
3.5.2 Attenuation (see 4.7.3). For the purpose of qualification testing, attenuation characteristic
requirements shall be as specified in 3.5.2.1. For the purpose of quality assurance testing, attenuation
characteristics shall be determined as specified in 3.5.2.2.
3.5.2.1 Qualification attenuation (see 4.7.3.1). The individual attenuation at each test center frequency
shall meet the requirements as specified (see 3.1). Mean attenuation values shall be rounded to the
nearest whole number.
3.5.2.2 Conformance inspection (see 4.7.3.2). The minimum attenuation requirements shall meet or
exceed the attenuation values determined at the time of initial qualification testing.
3.5.3 Speech intelligibility (see 4.7.4). The intelligibility scores shall meet or exceed the percentages
specified in table I, for the corresponding sound pressure test levels.
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