Specifications

MIL-STD- 1472E
5,3.7.4 Pre-emPhasis. If necessary, speech system input devices should employ frequency pre-
emphasis with a positive slope frequency characteristic no greater than 18 dB per octave from 140 to
1,500 to and no greater than 9 dB per octave over the frequency range 1,500 to 4,800 Hz, when no
clipping is used.
5.3.7.5 Peak+lir.minRofs
txzch simxals. Where speeeh signals arc to be transmitted over
channels showing less than 15 dB peak-speech to root-mean-square-noise ratios, peak clipping of 12
to 20 dB maybe employed at system input and may be preceded by frequency pre-emphasis as
specified in 5.3.7.4.
5.3.7.6 Noise shields. When the talker is in an intense noise field, the microphone should be
put in a noise shield. Noise shields should be meet the following requirements:
a.
b.
c.
d.
e.
A volume of at least 250 cu cm (15.25 cu in) shall be provided to permit
a pressure gradient
microphone to function normally.
A good seal shall be provided against the face with the pressure of the hand or the
tension of straps.
A hole or combination of holes covering a total area of 65 sq mm (O.1 sq in) shall be provided
in the shield to prevent pressure buildup.
Standing wave patterns shall be prevented by shape, or by use of sound absorbing
material.
The shield shall present no impediment to voice effort, mouth, jaw movement or breathing.
5.3.8 SLXX@I’CZ42DtiOnm ubment.
5.3.8.1 FHuencY rarwe. Headphones and loudspeakers shall be subject to the same frequency
response restrictions 8s microphom 8nd transmission qui~t except that hudspakers fbr use in
multi-speaker installations and multiple channels fed into headphones (e.g., where several speech
channels are to be monitonxi simultaneously) shall respond uniformly (A dB) from 100 to 4,800 Hz.
5.3.8.2 Loudspeakers for multi-channel monitoring.
5.3.8.2.1 Monitoring of speakers. If several channels are to be monitored simultaneously by
means of loudspeakers, the speakem shall be mounted at least 10“apart in the horizontal plane frontal
quadrant fiwm 45° ieft to 45° tight of the operator’s normal forward ikcing position.
5.3,43,2.2 F- Whenad&tic@
chatmel differentiation is requhui, apparent lateral
separation shall be enhaneai by applying low-pass filtenn~ (fre uency cutoff = 1,800 Hz) to signids
%
fed to loudspeakers on one side of the central operator position. three cbannek are invoIv4 one
channel shaIl be left unfiltered, a high pass filter with 1,000 Hz cutoff sIMIIbe provided in the second
channel, and a low-pass filter with 2$00 Hz cutoff shaJl be provided in the third channel. A visual
tigud shall be pmvidcd to show which channel is in use.
5.3.8.3 U= ofde-emphasm
When transmission equipment employs pre-emphasis and peak
Ciqq}ing i+ mx MA, wupkxl cq.uipmcnt dull employ frequency de-emphasis of characterist ics
complementary to tho,seof pre-emphasis only if it improves intelligibility, i.e., de-emphasis shall be a
negative-slop fkqueney response not grwter than 9 CMper oetuve cwerthe %eqt.uwy fwi~ MO k
4,MI0 H7