Security Classification 



DOCUMENT CONTROL DATA -R&D 



3/ title, body of abstract and indexing annotati 



be entered when the 



all report Is classified) 



JATING ACTIVITY (Corporate author) 



Arthur D. Little, Inc. 



2«. REPORT SECURITY C L A SSI F I C A T I C^ 



Unclassified 



26. GROUP 



3, REPOF 



The Measurement of Sound Speed in the Sea: Velocimeters and Other Devices 



1 VE NOTES (Type of repo 



. AU THOR(S) (First name, middle initial, last name) 



H. Francis Eden, Emma M. Duchane, Peter Von Thuna, and Richard H. Van Haagen 



6 REPORT DATE 



May 1967 



kL NO. OF PAGES 



63 



'b. NO. OF REFS 



39 



ia. CONTRACT OR GRANT NO. 



N00024-68-C-1137 



b. PROJEC T NO. 



SF-101-03-21 



9a. ORIGINATOR'S REPORT NUMSER(S) 



4330568 



0. DISTRIBUTION STATEMENT 



All distribution of this report is controlled. Qualified D.D.C. users shall request 

 through their cognizant codes to obtain the report. 



SUPPLEMENTARY NOTES 



12- SPONSORING MIL1TAF 



Dept. of the Navy 



Naval Ship Systems Command 



Data on the speed of sound in the sea is a prime requirement in Navy operations. 

 )nly relative accuracy in the measurements of sound speed as a function of depth is 

 leeded in tactical situations because it is the shape of the velocity profile that is 

 jf major importance to hull mounted sonar. Absolute accuracy in the measurement of 

 sound speed is desirable, however, in order to exploit longer range propagation in the 

 leep sound channel. 



The sound speed can be measured either indirectly, by computation from temperature 

 md salinity or density data, or directly, by using "velocimeters". In tactical 

 situations, temperature data alone has sufficed for the indirect method except under 

 ertain near shore conditions, where skilled guesswork has been required. 



Present velocimeters based on the "sing-around" principle are adequate for oceano- 

 raphic survey purposes, from the points of view of accuracy and depth capability, 

 lowever, their connecting cables render them unsuitable for tactical use; in general, 

 :he manufacturers of velocimeters are aware of and have been attempting solutions to the 

 Droblems that arise from this application. 



The value of temperature data alone for defining the presence of a surface duct in 

 shallow water where sharp salinity changes can occur should be studied. We believe that 

 :here exists a case for the development of an expendable instrument or of a synoptic 

 :echnique for tactical use to supplement the now successful expendable bathythermograph. 



DD 



1473 



Security Classification 



