MIL-DTL-9415B
4.5.3.5 Extreme operating temperature (see 3.14.1). The complete assembly shall be placed within a test
chamber wherein a temperature of + 71 degrees C (+ 160 degrees F) is maintained. The complete assembly shall be
exposed to this temperature for a period of 3 hours, at the conclusion of which, it shall be immediately transferred to a
chamber having an internal temperature of - 55 degrees C (- 67degrees F) and it shall be exposed to this
temperature for a period of 3 hours. The complete assembly shall be placed in the test chamber with the face of the
loudspeaker exposed and shall be operated at 400 Hz with a signal input of 2.65 volts to the amplifier throughout the
test. The complete assembly shall be inspected for evidence of mechanical impairment after the test. The
impedance, sensitivity, response-frequency characteristic of the loudspeaker, the gain, and distortion of the amplifier
shall be measured before the test, during the test, and within 1 hour after the test.
4.5.3.6 Temperature cycling (see 3.14.2). The complete assembly shall be placed in the test chamber with the
face of the loudspeaker exposed. The complete assembly shall be exposed to a temperature of + 85 degrees C (+
185 degrees F) for 1 hour, placed in room temperature for 15 minutes, then exposed to a temperature of 65
degrees C (- 85 degrees F) for 1 hour, and again placed in room temperature for 15 minutes. The complete
assembly shall be subjected to ten such temperature cycles. The complete assembly shall be inspected for evidence
of mechanical impairment after the test. The impedance, sensitivity, and response-frequency characteristic of the
loudspeaker, the gain, and distortion of the amplifier shall be measured before the test, immediately after the + 85
degrees C exposure and 65 degrees C exposure during the last cycle, and 1 hour after completion of the test.
4.5.3.7 Pressure cycling (see 3.14.3). The complete assembly shall be placed in the test chamber with the face of
the loudspeaker exposed and the absolute internal pressure of the chamber reduced to 3.44 inches of mercury
(corresponding to an altitude of 50,000 feet above sea level) and allowed to remain at the reduced pressure for 5
minutes. The pressure shall be increased again to that prevailing at ground level and the complete assembly be
allowed to remain at atmospheric pressure for 5 minutes. The rate of change of pressure shall correspond to
approximately 50,000 feet per minute. The complete assembly shall be subjected to three such pressure cycles and
shall be operated at 400 Hz with a signal input of 2.65 volts to the amplifier throughout the test. The complete
assembly shall be inspected for evidence of mechanical impairment after the test. The impedance, sensitivity, and
response-frequency characteristic of the loudspeaker and the gain and distortion of the amplifier shall be measured at
ground level before the test, and immediately after the test.
4.5.3.8 Humidity (see 3.14.4). The complete assembly loudspeaker shall be subjected to humidity testing in
accordance with method 507 of MIL-STD-810. The following details and exceptions shall apply:
a. Procedure I.
b. Measurements after the test. The complete assembly shall be inspected for evidence of mechanical
impairment after the test. The impedance, sensitivity, and response-frequency characteristic of the
loudspeaker and the gain and distortion of the amplifier shall be measured before the test, within 1 hour after
the test, and 24 hours after the test.
4.5.3.9 Vibration (see 3.14.5). The complete assembly loudspeaker shall be tested in accordance with method
514 of MIL-STD-810. The following details and exceptions shall apply: The amplifier and the loudspeaker shall be
turned on but no signal shall be applied.
a. Procedure - 1, part 1.
b. Categories 7, 8, and 9. (Aircraft, jet, propeller and helicopter).
c. The voltage across the loudspeaker shall be read during vibration. The maximum voltage measured during
the test shall be taken at the microphonic noise output of the amplifier.
d. The complete assembly shall be inspected for evidence of mechanical impairment after the test.
e. In addition, the impedance, sensitivity, and response-frequency characteristic of the loudspeaker and the gain
and distortion of the amplifier shall be measured before the test and within 1 hour after completion of the test.
f. The loudspeaker lead connector shall be inspected for proper engagement after the vibration test.
4.5.3.10 Shock tests (see 3.14.6).
4.5.3.10.1 Shock test (15g). The complete assembly shall be mounted securely to the shock testing machine and
subjected to five shocks of 15g, each having a time duration of 11 milliseconds ±1 millisecond, in each of the
following directions:
a. Each of two directions parallel to the length dimension.
b. Each of two directions parallel to the width dimension.
c. Each of two directions parallel to the height dimension.
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