234 



VOICE COMMUNICATION, I 



very difficult to pass messages in the face of 

 masking noises with the desired speed and 

 accuracy. The chain of communication in- 

 corporates people and speech, as well as 

 telephone equipment, and, like other chains. 



130 

 120 

 110 

 100 

 90 



eo 



70 

 60 

 60 

 40 



OA. 



f<75 75 150 30O 600 l?00 2400 f>4e00 

 ISO 300 600 1200 2400 4800 



FREQUENCY OCTAVES IN CPS. 



CD S 

 CI > 



f<75 75 IbC 300 600 IcOO 2400 f>4600 

 150 30"; 600 1200 Z'-OO -4800 



FREQUENCY OCTAVtlS IN CPS 



Fig. 1. Examples of noise spectra found in USS 

 REDFISH. The symbol O.A. refers to overall 

 sound pressure level. The sound pressure levels 

 measured in successive bands one octave wide 

 are shown by the points on the curves. 



it is no stronger than its weakest link. Both 

 the human and vocal links must be utilized 

 to their utmost efficiency if we are to avoid 

 the danger of critical failures in the operation 

 of a submarine. 



There are three ways in which the quality 

 of the human and vocal elements in com- 

 munication can be considerably improved; 



1. Operators manning the more important 

 communication posts can be selected for 

 their inherent ability to speak intelligibly, 

 as well as to interpret messages which have 

 been altered by distortion and partially 

 masked by noise. 



2. All operators can be trained to speak 

 more intelligibly, to use their equipment efl&- 

 ciently, and to improve their ability to in- 

 terpret mutilated vocal signals. 



3. All important messages can be stand- 

 ardized, so that — without departing too far 

 from conrnaon usage — they are short, simple, 

 easy to say, and easy to understand. 



Considerable progress was made by the 

 Submarine Service along all three of these 

 lines in the late stages of the last war. This 

 chapter will describe these developments, 

 and, in addition, will summarize the existing 

 knowledge about these matters, as an aid 

 both in consohdating existing gains and in 

 formulating a program for further research 

 and improvement in the future. 



It should be emphasized at the start that 

 routine tests for acuity of hearing, standard 

 criteria of "good speech," and conventional 

 methods for rating and training public 

 speakers, however valuable for the concerns 

 of everyday life, are not valid for the peculiar 

 conditions of military communication in 

 noise. The criterion here is not "effective- 

 ness," "pleasantness," nor any aesthetic 

 quality, but the one crucial attribute: can 

 what is said be heard and understood? For 

 the most part knowledge of the attributes of 

 speech, speakers, and listeners, conducive to 

 efficient communication in noise, had to be 

 discovered by special experimentation during 

 the last war. 



//. The Selection of Communications Oper- 

 ators 



Tests for Listeners. Human beings differ 

 greatly in their abihty to make out a message 

 which has been distorted by imperfect equip- 

 ment and partially drowned out by interfer- 



