MIL-DTL-21393B
3.6.13 Humidity (see 4.6.3.10). The microphone shall resist degradation in performance, due to
exposure to extremes of a warm, humid atmosphere, resisting such defects as corrosion, biological
growth, material property changes due to moisture penetration, and effects of condensation. Following
such exposure, the product shall exhibit the following performance:
Visual examination:
No evidence of physical damage, which would cause a
malfunction.
Sensitivity and frequency response:
No more than ± 3 dB variation at any frequency.
3.6.14 Temperature cycling (see 4.6.3.11). When tested, the product shall exhibit the following
performance:
Sensitivity and frequency response:
No more than ± 3 dB variation at any frequency.
3.6.15 Temperature extremes (see 4.6.3.12). When tested, the product shall exhibit the following
performance:
Sensitivity and frequency response:
No more than ± 3 dB variation at any frequency.
3.6.16 Salt fog (see 4.6.3.13). The microphone shall be capable of operation in salt atmosphere as
encountered in coastal areas. Prolonged periods of exposure to salt sea atmosphere shall not result in
visible evidence of corrosion on any equipment surfaces. Following exposure to an extreme salt
atmosphere, the product shall exhibit the following performance:
Visual examination:
No evidence of physical damage, which would cause a
malfunction.
Sensitivity and frequency response:
No more than ± 3 dB variation at any frequency.
4. VERIFICATION
4.1 Classification of inspections. The inspection requirements specified herein are classified as
follows:
a. First article inspection (see 4.3). First article tests are those tests accomplished on samples
submitted prior to a production run, for approval as a satisfactory product.
b. Conformance inspection (see 4.5). Acceptance tests are those tests accomplished on
microphone units manufactured and submitted for acceptance under a contract.
(1) Group A (Individual) tests. Individual tests are those tests conducted on each
equipment submitted for acceptance under the contract.
(2) Group B (Sampling) tests. Sampling tests are those tests accomplished on a
quantity of equipments, as approved by the procuring activity, and which have
previously passed Individual tests.
c. Reliability test (see 4.7). When required, the reliability test shall be conducted by the contractor
and within the contractor's plant. These tests shall be conducted, as part of the first article
inspection and/or conformance inspection, when specified within the contract (see 6.2d and e).
4.1.1 Standard/Service conditions. The following conditions shall be used as a basis to establish
normal performance requirements and for making laboratory bench tests on the microphone.
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