MIL-DTL-5794C
3.5.5 Burning noise (see 4.6.5). The output of the microphone unit, due to burning noise, shall be kept
to the lowest practicable minimum and in no case shall it exceed 1.0 millivolt.
3.5.6 Vibration aging characteristics (see 4.6.13). The design and construction of and the materials
used in the microphone unit shall be such that the microphone unit shall maintain its original performance
characteristics, in use or in storage. The microphone unit shall comply with the following requirements,
when artificially aged as a result of the vibration tests.
3.5.6.1 Change in resistance due to aging. The resistance of the microphone unit shall not increase by
more than 75 percent of its original resistance, as a result of the prescribed vibration tests.
3.5.6.2 Change in response due to aging. The average response of the microphone unit over the 300
to 4,000 Hz frequency range shall not change by more than 3 dB, as a result of the vibration tests.
3.5.7 Anti-packing (see 4.6.16).
3.5.7.1 Surges. The microphone unit shall retain its response characteristics within 4 dB, after 10
interruptions of the current, in the test circuit on figure 3. The following test conditions apply:
a. 50 millihenry inductance.
b. make-break switch added in series with the microphone unit.
c. microphone current adjusted for 50 milliamperes.
3.5.7.2 Overload current. The microphone unit shall be capable of retaining its response
characteristics within 3 dB immediately after being subjected to a dc excitation of 80 milliamperes for 1
(one) hour in a constant current circuit.
3.5.7.3 Extended operation. The microphone unit shall be capable of retaining its response
characteristics within 4 dB, immediately after being subjected to an excitation current of 50 milliamperes
for 8 (eight) hours in a constant current circuit.
3.5.8 Immersion (Microphone, Carbon M-51/UR). The response of the microphone shall not
decrease by more than 3 dB from its initial response, at any frequency between 300 and 4,000 Hz after
immersion (see 4.6.12).
3.5.9 Gun blast (Microphone, Carbon M-51/UR). The microphone shall transmit intelligible speech
after subjection to the gun blast test (see 4.6.14). The degradation in response shall not exceed 4 dB at
any frequency.
3.6 Service conditions (Environmental).
3.6.1 Altitude.
3.6.1.1 Microphone Unit M-6A/UR.
3.6.1.1.1 Response during pressure changes within operating range (see 4.6.8.2). The response of
the microphone unit shall not vary by more than 3 dB from its initial response at any frequency between
300 and 4,000 Hz, when subjected to any pressure in the range of 30 to 16.7 inches of mercury
(simulation of ground level to approximately an altitude of 15,000 feet) inclusive, with the pressure
constant or varying.
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