Specifications

MIL-STD-1472E
a.
b.
c.
The standard method of measuring phonetically balanced (PB) monosyllabic word
intelligibility, ANSI S3.2, should be used when high test sensitivity and accumcy are
required.
The modified rhyme test (MRT) (see Human Engineering Guide to Equipment Design)
should be used if the test requirements are not as stringent or if time and training do not permit
the use of the ANSI method.
Articulation index (AI) calculations should be used for estimations, comparison and
predictions of system intelligibility based upon ANSI S3.5.
5.3.12.2 Criteria The intelligibility criteria shown in Table VI shall be used for voice
communication. The efficiency of communications needed and the type material to be transmitted shall
determine which of the three communication requirements of Table VI is to be selected.
TABLE VI. Intelligibility criteria for voice communication systems
COMMUNICATION REQUIREMENT
SCORE
PB
IMRTI AI
I Exceptionally high intelligibility; separate syllables understood
I 90% I 9770 I 0.7
Normal acceptable intelligibility; about 98% of sentences comctly
heard; single digits understood
II
75% 91% 0.5
1
I
I I
Minimally acceptable intelligibility; limited standardize phrases
understood; about 90% sentences cornxtl y heard (not acceptable for 43%
75% 0.3
operational quipment)