in industry,, and especially the experience gained by U. S« and 

 British Navy laboratories during the years between the two 

 World Wars, 



At the outset it was, of course _„ impossible to forecast 

 all the types of acoustical devices that developments in the 

 military situation would require,, The program,, therefore,, 

 was as broad in its scope as possible,, 



The work on standardization sought not only the devel- 

 opment of instruments and techniques required for precision 

 measurements j, but in addition careful consideration was given 

 to the establishment of standard terms, basic units and refer- 

 ence points, so that the results of all quantitative measure- 

 ments could be accurately and conveniently expressed. 



The work was carried forward actively throughout the war 

 and • 



men 



made with a pr 



in air acoustics,, 



At the war's outset, no single type of underwater acoust- 

 ical device was sufficiently reliable to serve either as a 

 standard hydrophone or a standard source of sound,, At the 

 close of the war, acoustic systems of the greatest versatility 

 and efficiency were in use and under development „ At each 

 stage in the evolution of these devices^ corresponding im- 

 provements were called for in the standardizing techniques 

 and instrumentalities needed for precision measurements „ 



Equally important to the specification of test equipment 

 for the work was the formulation of measurement techniques 

 and calculation routines „ First in importance was the choice 

 of frequency range in which calibrations were to be made „ In 

 the beginnings this range was from 100 cycles per second to 

 50 kilocycles per second" by the close of the war it extended 

 from 2 cycles per second to 2„2 megacycles per second,, 



Provision was made for the study of the effect of other 

 pertinent physical factors on performance such as the temper- 

 ature and pressure conditions encountered by gear in the ocean. 

 This included the ability to produce temperature variations 

 similar to those encountered in both the arctic and tropical 

 regions, as well as to reproduce the hydrostatic pressures 

 to which a submerged submarine is subjected during actual 

 operations o 



31 



