other special signals have resulted in refinements in the art 

 of instrument design and associated electrical circuits that 

 promise to find many useful applications . 



Acoustics of Wakes. 



When the development of measures to counter the enemy's 

 acoustic torpedoes became urgent^ it was obvious that the 

 acoustic properties of wakes would determine the success or 

 failure of these devices The sound output of the ship's 

 screws was also an essential datum Consequently, basic re- 

 search on the properties of wakes became a high priority task 

 assigned to UCDWR and to other groups working under Division 6„ 



Pro- submarine Rese arch , 



As with other parts of the Division 6 program, as the war 

 progressed^ the basic research program was able to turn from 

 anti-submarine operations to pro-submarine operations A 

 scientific study was undertaken of the effect of subsurface 

 weather on the diving operations of our own submarine s 



Special submarine supplements to the sailing directions 

 published by the Hydrographic Office included not only infor- 

 mation on diving and sound conditions, but also on wind and 

 water currents,, bottom topography and character and so on. 

 All three NDRC groups that were participating in the program 

 cooperated in the preparation of the supplements and a special 

 group of writers and cartographers was established at San Diego 

 headed by a geologist on leave from the Geological Survey of 

 the Department of the Interior Numerous other special charts 

 were prepared by NDRC personnel, among them a series of bottom 

 sediment charts and special charts requested in connection 

 with amphibious operations „ 



Oceanographic factors also played an important part in 

 the design, location and operation of harbor defense equip- 

 ment, especially in the location of listening hydrophones and 

 echo-ranging gear mounted on the ocean bottom On both the 

 Atlantic and Pacific coasts, NDRC laboratories collaborated 

 with the Navy in special acoustic surveys designed to obtain 

 useful information applicable to harbor approach areas „ 



The use of fundamental oceanographic data to improve the 

 basic design of sonar gear, while less widespread than the 



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