FOREWORD 



One of the principal responsibilities placed upon 

 Section C-4, later Division 6, when it was organ- 

 ized in 1911 was that of developing new and improved 

 methods for detecting submerged submarines. Ex- 

 perience had shown that sound is the only form <>l 

 energy which can be propagated through sea water 

 with sufficient intensity and range to serve as a prac- 

 tical method for detection. For this reason the Section 

 initiated at once a thorough study of the acoustical 

 properties of sea water as well as of methods for in- 

 jecting sound energy into the water and of detecting 

 its presence there. Realizing that in a study of this 

 kind accurate measurement in terms of known and 

 reproducible standards is essential, the Section under- 

 took early in 1941 to develop a number of standard 

 projectors and hydrophones covering the useful fre- 

 quency ranges and capable of being accurately cali- 

 brated in terms of energy output or input. Further, 

 the Section undertook to develop methods for cali- 

 brating these standards and methods applicable to 

 the accurate testing of underwater sound gear under 

 development or in production by various Govern- 

 ment agencies. This activity was at first conducted 

 under a contract at the Bell Telephone Laboratories, 

 which established two calibrating and testing labora- 

 tories, the first at Mountain Lakes, New Jersey, and 

 somewhat later a second at Orlando, Florida. The 

 facilities of these two laboratories were made avail- 

 able to all organizations developing or manufactur- 

 ing sound gear for the Navy. 



In 1942 the operation of these two stations together 

 with the responsibility for certain further develop- 

 ment of methods was transferred, along with many of 

 the experienced personnel, from the Bell Telephone 

 Laboratories to the Columbia University Division of 

 War Research contract. The former organization, 

 however, continued the further development and 

 particularly the construction of standard instruments 

 which have found wide use. From the time of trans- 

 fer, the organization carrying on operations centering 

 at Mountain Lakes and Orlando was known as the 



Underwater Sound Reference Laboratories and was 

 under the direction of Dr. Robert S. Shankland. 



In addition to the two above-mentioned testing 

 stations, various of the Division's other contractors 

 found it necessary to establish at suitable locations 

 less elaborate testing laboratories to facilitate the test- 

 ing of sonar devices, systems, and methods at various 

 stages of their development. 



The material in this report prepared by members 

 of the staff of the Underwater Sound Reference Labo- 

 ratories describes the methods and procedures which, 

 as a result of over four years development and ex- 

 perience, the Division believes can be followed in 

 establishing and operating a sound reference labora- 

 tory. The possible scope of such a laboratory is indi- 

 cated by including a description of its activities since 

 its operation under the Columbia University Divi- 

 sion of War Research. 



In addition to the persons whose names appear as 

 authors of chapters or sections of this report, many 

 others have made important technical contributions 

 to this development. 



The four-year program covered by this report owes 

 much to the continuous liaison furnished by the 

 Navy. The Division expresses its appreciation for the 

 most helpful and cordial support and cooperation 

 received from the Office of the Coordinator of Re- 

 search and Development and from the Bureau of 

 Ships (940). A list of the principal Navy projects is 

 furnished on page 171. 



Manufacturers producing or developing sonar 

 material under Navy contracts have in many and 

 various ways cooperated wholeheartedly. In particu- 

 lar, members of their staffs gave freely of their time to 

 the work of the Hydrophone Advisory Committee ap- 

 pointed by the Office of the Coordinator in April, 

 1942. On page 172 the structure and the general scope 

 of this committee are outlined. 



John T. Tate 

 Chief, Division (i 



