By keeping in constant touch with the Services and the 

 NDRC and industrial laboratories developing new equipment, 

 the Underwater Sound Reference Laboratories were able to 

 anticipate well in advance the kinds of precision measure- 

 ments they would be called upon to make 



The expansion of testing facilities which this policy 

 required ultimately made available four complete calibrating 

 systems for the frequency range from 20 cycles per second to 

 150 kilocycles per second; two of these systems being in- 

 stalled at Mountain Lakes, New Jersey^, and two at Orlando, 

 Florida „ 



Research and development work on standardization was 

 carried on along both theoretical and experimental lines „ 

 The theoretical program included the definition and adop- 

 tion of standard terms and units for expressing the results 

 of underwater sound measurements, and rating the efficiency 

 and performance of acoustical devices. Theoretical and ex- 

 perimental work was carried on for the specification of 

 optimum testing depths s and distances; and a schedule of 

 computation procedures for accurate and rapid preparation of 

 the test data in report form* The choice of terms and units 

 was adopted with the aid of a Hydrophone Advisory Committee 

 appointed by the Coordinator of Research and Development of 

 the Navy The definitions and terms finally adopted have been 

 recommended by the Navy for adoption by the American Stand- 

 ards Association for underwater soundo 



The classes of acoustical gear upon which calibrations 

 and tests were made by the USRL in Lhe course of the war in- 

 cludes echo ranging sonar; shipboard and submarine listen- 

 ing systems; acoustic elements for the radio sonobuoy; harbor 

 defense installations; and quality control instruments. 



Among the wide variety of new acoustical techniques per- 

 fected during the war may be cited the use of enclosed test- 

 ing tanks where side wall reflections were eliminated by the 

 use of short pulsing techniques utilizing developments in 

 radar circuits „ Without these methods a large number of 

 calibration and factory production test procedures would 

 have been wholly impractical . 



Suring the period of operation of the Underwater Sound 

 Reference Laboratories by Division 6 S the resulting improve- 

 ments in quantitative measuring and standardizing techniques 

 were made available to all authorized organizations „ This 



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