MIL-PRF-26542F
3.4.5 Cable assemblies. Unless otherwise specified (see 3.1), cord assemblies shall meet either of the
2 two) following requirements, to ensure a quality interfacing product.
a. The use of QPL cord assemblies referenced in MIL-DTL-22442.
b. Verification and approval by the qualifying activity of meeting the technical requirement of
MIL-DTL-22442.
NOTE: Both of the above methods require qualification of the entire specification product to the
applicable qualification requirements.
3.4.6 Weight. Weight shall be as specified (see 3.1).
3.5 Performance. Parameter applicability shall be as specified (see 3.1). Performance variations
allowable, following subjection to environmental exposures, shall utilize the initial group 1 measurements
as a reference. Performance variations are not cumulative with multiple environmental exposures. See
3.5.2 Sensitivity at altitude (see 4.5.2.3). When applicable, the sensitivity at the simulated altitude shall
be as specified (see 3.1).
3.5.3 Frequency response at ground level (see 4.5.2.4). The frequency response of the microphone
shall be within the frequency response limits specified (see 3.1).
3.5.4 Frequency response at altitude (see 4.5.2.5). When applicable, the frequency response at the
simulated altitude shall be as specified (see 3.1).
3.5.5 Impedance (see 4.5.3). The impedance at any frequency over the specified frequency response
range (see 3.1) shall not deviate from the impedance at 1,000 Hz by more than 10 percent, unless
otherwise specified (see 3.1).
3.5.5.1 Impedance limits (see 4.5.3). The impedance at 1,000 Hz and at 20 degrees C (68 degrees F)
shall be as specified (see 3.1).
3.5.6 Total harmonic distortion (see 4.5.4). Unless otherwise specified (see 3.1), the total harmonic
distortion in the output of the microphone within the specified frequency response range (see 3.1) shall
not exceed 6 percent with an input sound pressure of 114 dB relative to 20 micropascals (µPa).
3.5.7 Signal-to-acoustic noise (see 4.5.5). For the purpose of qualification, the noise cancellation
characteristics shall be in accordance with 3.5.7.1. For the purpose of quality assurance, the noise
immunity characteristics shall be in accordance with 3.5.7.1 or 3.5.7.2 at the manufacturer's option. The
microphone shall discriminate in favor of speech signals and against acoustic noise.
3.5.7.1 Noise cancellation characteristics (see 4.5.5.1). The noise cancellation characteristic of the
microphone shall be such that the "average difference curve" and the peaks of the "difference curve A"
and "difference curve B", derived from the frequency response characteristics of the microphone to a
"close" and "distant" sound source as specified herein, shall fall within an envelope having a slope of not
less than 6 dB per octave falling between 200 Hz and 4,000 Hz. The "difference curve A" and the
"difference curve B" may go through the envelope on the lower side. But, they shall not go through the
envelope on the top side. The centerline of the envelope shall intersect the zero axis, between 5,000 Hz
and 8,000 Hz.
3.5.7.2 Noise-immunity characteristic. Under standard conditions, the signal-to-noise ratio shall be at
least 15 dB in favor of the signal, when measured in accordance with 4.5.5.2.
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