238 



VOICE COMMUNICATION, I 



cial requirements of audibility in noise . (See 

 Fig. 4.) For example, a list of words chosen 

 at random was found, under stress of noise, 

 to be correctly identified only half as often 

 as a list of 1000 words selected b}^ special 

 experiment (7, p. 60). The success of com- 

 munications can be aided very materially 

 by the use of words, kno-wn to be highly 

 audible in noise, as standard components 

 of all basic messages and procedures. Au- 

 dibiUty, though not the sole, is the indispen- 



-I — I — ! — r- 



^^ 



10 20 30 40 50 60 70 80 90 lOO 



PERCENT AUDIBILITY RATINGS 



Fig. 4. The distribution of ratings for 1600 

 words. Each column represents a 5-percent range 

 of audibility. The height of the column shows 

 the number of words falling within each range of 

 audibility. The 1000 most audible words are 

 those which fall to the right of Line A. Line B 

 indicates the average audibility for a separate list 

 of 300 monosyllables and dissyllables chosen at 

 random. This represents the average score to be 

 expected for common words chosen without 

 reference to audibility. 



sable attribute of a military vocabulary. If 

 a message is not understood, its other virtues 

 will avail it nothing. 



Existing List of Standard Submarine Phra- 

 seology. In 1944, the NDRC collaborated 

 with the Submarine Service to develop a 

 handbook standardizing both voice proce- 

 dures (methods for calling telephone stations 

 and formulating commands, acknowledg- 

 ments, and reports) and phraseology (spe- 

 cific wordings for all important submarine 

 messages). It was recognized that such 



standardization would improve the speed 

 and accuracy of voice communications. 

 The talker who has learned a single phrasing 

 for each routine message does not hesitate 

 or fumble for words. The listener who 

 knows in advance that each message is one 

 of a very small number of possibilities has 

 less difficulty in making out what he hears. 

 Men transferred from one ship to another 

 need not waste time nor confuse themselves 

 by learning a new terminology (24, pp. 7-12). 

 Four criteria were used to select a stand- 

 ard submarine phraseology: 



1. Conformity to common submarine us- 

 age. The final set was chosen from lists of 

 orders and commands submitted by more 

 than twenty submarine commanders. 



2. Audibility in noise. Alternative sta- 

 tion call-names and other key words and 

 phrases were tested for their relative iden- 

 tifiability over sound-powered phones in the 

 presence of a simulated submarine diesel 

 noise. 



3. Freedom from a tendency to confusion. 

 When, in the audibility tests, listeners were 

 found consistently to mistake one message- 

 component for another word of similar pho- 

 netic properties, one of these was omitted 

 from the final list. Thus, the word "shut" 

 was chosen over the alternative form, 

 "close," because fisteners tended to a dan- 

 gerous degree to confuse "close" with the 

 other commands, "open" and "blow." 



4. Brevity and ease of pronunciation. 

 With other things equal, the simple, succinct 

 message was preferred over a longer or more 

 cumbersome alternative. 



The final list of procedures and messages 

 was adopted in a series of conferences atten- 

 ded by a large number of submarine and 

 division commanders. This list was issued 

 and distributed by the Commander, Sub- 

 marines, Atlantic Fleet, in a handbook en- 

 titled Standard Submarine Phraseology. 



Factors Governing the Audibility of Words. 

 As the construction, the equipment, and the 

 routine operation of submarines change, it 

 will prove necessary to modify and supple- 



