UR.

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MIL-DTL-5794C

3.4.4 Weight. The weight of a microphone unit shall not exceed one ounce.

3.4.5 Carbon and carbon cavity.

3.4.5.1 Carbon granules. The carbon granules shall be of a grade, quality, size, and shape equivalent

to Western Electric type 13A122 and shall be suitable in every respect, for the particular application.

3.4.5.2 Carbon granule leaks. The carbon granules shall be retained positively in the microphone unit

in such a manner that it is impossible for them to leak from the carbon cavity during normal service use or

under any of the conditions specified herein.

3.4.5.3 Carbon cavity. All contact surfaces within the carbon cavity shall be suitably plated with gold,

and shall be free from porosity, and shall be thoroughly cleaned before assembly of the microphone.

3.5 Performance.

3.5.1 Response characteristics. The response of the microphone unit measured as specified herein

shall be expressed in decibels (dB) relative to a zero reference level of 1.0 millivolt. The sound pressure

applied to the face of the microphone unit shall be 115 dB and relative to 20 micro-Pascal (�Pa). The

response shall be such as to meet the following requirements, when measured with the grid of the

microphone unit in a vertical plane.

3.5.1.1 Response limits � Microphone M-6A/UR. The frequency response shall be not less than 45

dB, nor more than 53 dB, at any frequency between 300 and 4,000 Hz, inclusive. The arithmetical

average of the test frequency response values over the 300 to 4,000 Hz frequency range shall be

between the limits of 47.0 and 51.0 dB, inclusive. The difference between any two successive readings,

200 cycles apart, shall not exceed 2.5 dB. Below 300 and above 4,000 Hz, the response shall fall off at a

rate of not less than 3 dB per octave.

3.5.1.2 Response limits � Microphone, Carbon M-51/UR. The response shall be not less than 45 dB

above a zero reference level of 1 millivolt across 100 ohms at 1,000 Hz and shall meet the frequency

requirements listed in table I and table II, when the microphone unit is in the vertical position.

3.5.1.2.1 Smoothness of frequency response curve. The response, within each frequency band

shown in table II, shall not vary by more than the specified rate of change in dB, when measured across

any band width of the specified size.