3-01This specification covers 2 \(two\) hand-held Dynamic Microphones, with or without a self-contained transistor amplifier and different connectors for use in unique military equipment. A wall-mounted holder is also included.

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MIL-DTL-21393B

4.6.3 Test methods. Tests required by this specification shall be conducted in accordance with the

following procedures.

4.6.3.1 Visual and dimensional inspection (see 3.2, 3.3, and 3.4). Each sample selected shall be

examined externally to determine conformance with this specification with respect to material,

workmanship, design, weight and dimensions.

4.6.3.1.1 Retractile cordage test methods (see 3.5.2). The cord shall be tested in accordance with

MIL-DTL-55668.or an equivalent, which shall be approved by the procuring activity.

4.6.3.1.2 Anchorage (see 3.5.2.1). While anchored at the microphone and at the connector, the

cordage and the connections shall have a 20-pound axial load applied, for a period of 5 (five) minutes.

4.6.3.2 Performance requirements (see 3.6). Response measurements for sensitivity, frequency

response, linearity, and microphone current shall be made, utilizing the test circuit on figure 2.

4.6.3.2.1 Sensitivity (see 3.6.1). The output of the microphone shall be measured at a sound pressure

level of 115 dB above 20 �Pa and at a frequency of 1000 Hz, utilizing the test circuit on figure 2.

4.6.3.2.2 Frequency response (see 3.6.2). Each microphone unit shall be subjected to response tests

at no less than 6 approved frequencies, such as 300, 1000, 2000, 3000, 4000 and 6000 Hz. The

specified frequencies to be used will be determined by the procuring activity on the basis of tests made

and information gained in the initial stages of production. Sweep or band frequency tests may be

employed provided the contractor demonstrates the suitability of such tests to the procuring activity. The

method of testing and the selection of frequencies shall be such that they will truly indicate the over-all

response characteristics and output level of the microphone.

4.6.3.2.3 Linearity (see 3.6.3). The output of the microphone shall be measured during variation in the

input sound pressure level across the range of 80 dB to 125 dB above 20 �Pa.

4.6.3.2.4 Microphone current (see 3.6.4). The microphone current shall be measured, utilizing the test

circuit on figure 2.

4.6.3.3 Voltage transients test (see 3.6.5). The microphone shall be subjected, through its output plug,

to 350-volt pulses having a width of approximately 500 microseconds and a repetition rate of 2 pulses per

second (pps). The pulses shall be applied for a period of five minutes in each polarity. The microphone

shall be inactive during this test.

4.6.3.4 Signal-to-noise ratio (see 3.6.6 and 4.6.1.4). The microphone under test shall be mounted in a

test apparatus similar or equal to that shown on figure 3, with the front grid of the microphone � inch from

the mouth of the signal speaker. With the microphone under test connected to the test circuit similar or

equal to that shown on figure 4, the noise spectrum shall be applied and the microphone output

measured. The noise spectrum shall be removed and the signal spectrum applied. The output of the

microphone shall be measured. The signal-to-noise ratio shall be the quotient of these measured values.

4.6.3.5 Radio interference control (see 3.6.7). With the microphone under test connected as shown on

figure 6, interference tests shall be conducted in accordance with MIL-STD-461, for (internal) applications

on submarines (Navy) and aircraft (Air Force and Navy).

4.6.3.5.1 Radiated emissions. The procedures of RE102, Radiated Emissions, Electric Field, and 10

kHz to 18 GHz shall be applied to the microphone under test (see MIL-STD-461).