Specifications

I
MM’I’’D-1472E
5,3.2.4 Relation to visual dis~lays, When used in conjunction with visual displays, audio
warning devices shall be supplementary or supportive. The audio signal
shall be used to alert and
direct operator attention to the appropriate visual display,
5.3.3 Characteristics of audio wamin~ simmls.
5.3.3.1 Freuuency.
5.3.3.1.1 Rarme. The frequency range shall be between 200 and 5,000 Hz and, if possible,
between 500 and 3,000 Hz. When signals must travel over 300 m (985 ft), sounds with fnquencies
below 1,000 Hz should be used. Frequencies below 500 Hz should be used when signals must bend
around obstacles or pass through partitions. The selected frequency band shall differ from the most
intense background frequencies and shall be in accordance with other criteria in this section.
5.3.3.1.2 Electric power
fnxmency avoidance. The frequency of a warning tone shall be
different from that of the electric power employed in the system.
5.3.3.2 Intensity.
5.3.3.2.1 CornpatibiliW with acoustical environment. The intensity, duration and source
location of audio alarms and signals sh~ be compatible with the acoustical environment of the
intended receiver as well as the requirements of other personnel in the signal axeas.
5.3.3.2.2 Comatibilitv with clothim and euuimnent. Audio signals shall be loud enough to be
heard and understood through equipment or gaments (e.g., parka hood, NBC protective hood,
hearing protective devices) covering the ears of the listener.
5.3.3.2.3 Discomfort. Audio warning sigmds should not be of such intensity as to cause
discomfort or “ringing” in the ears.
5.3.4 Signal c~
“ “Csirtrelation tocnlemtl“Onalu)nditions and Objectives.
5.3.4.1 Audibil&y. A signal-@noise ratio of at least 20 dB shall be provided in at least one
octave band between 200 and 5,000 Hz at the operating position of the intended receiver.
5.3.4.2 Alertirm
camdility.
5.3.4.2.1 Attention- Signals with high alerting capacity should be provided when the system or
equipment requires the opemtor to eommmte amniort.
Such signals shall ~ imwever, be so
startling as to preclude appropriate responses or interfere with other functions by holding attention
mveyfrwnetherorA.iod@ruda.
5.3,4.2.2
Onset and SOLUAd
mssure
level. The onset of critical alerting signals should be
sudden, and a relatively high sound pressure level should be provided as specified 5.3.4.1.
5.3.4.2.3 Dichotic uresataho“ n. When earphones will be worn in the operational situation, a
dichotic presentation should be used whenever feasib~e,alternating the signal from one ear to the other
hy means of a dual-channel headse(.
5 24. z 4 He~dset, When the operator is Wetiring earphones c~verin~ Wh ears during normal
equipment opera-e audio warning signal shall be directed to the operator’s headset as well as to
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Rinatlrol hedwts should not he used in any opcrntinnal environment helm R5dRA
WhCIC souIIds t.hut prm’ide llw operator with useful information cannot bc dircc(ed to the operator’s