Many combat vessels transmitted to the researchers data 

 which were incorporated into the general pattern of the find- 

 ings o On the basis of all the facts thus at hand, the research 

 workers were able to prepare sound ranging charts which gave 

 a general indication of the conditions which might be expected 

 to be found in various areas Published by the Hydrographic 

 Office p these charts were disseminated widely throughout the 

 Fleets and were used in the planning of antisubmarine opera- 

 tions and in the routing of convoys With the development of 

 better methods of predicting maximum echo ranges , not only 

 could the commanding officer of a convoy plan the best dis- 

 position of his escort vessels , but the sonar operator could 

 use the information to determine the best settings of the 

 dials on his gear and plan his search operations more effec- 

 tively,, A bathythermograph on at least one escort vessel of 

 every convoy or other unit became standard equipment g and a 

 standard form of "sonar message" was devised to transmit 

 sound range predictions to other escort vessels , 



While the transmission program was one of the most im- 

 portant phases of the basic research carried out by NDRC, it 

 was by no means the only one „ Measurements of the noise out- 

 put from ships and submarines, calibration measurements on 

 all types of sonar gear, the acoustic properties of wakes - 

 these were among the many subjects studied for various 

 special purposes 



Ships, Submarines aid Marine Life as Sound Sources. 



Studies were made of the characteristics of ships and 

 submarines as sound sources,, Hundreds of measurements were 

 made of the sound output of all types of vessels, ranging 

 from submarines to battle ships and aircraft carriers „ These 

 were important in the design of acoustically actuated under- 

 water mines and also in the computation of maximum listening 

 ranges obtainable with Navy sonar gear, 



One collateral observation showed that some carriers had 

 "singing" propellers o It was found that by a relatively minor 

 change in propeller design this very undesirable type of sound 

 could be eliminated,, A number of general conclusions of per- 

 manent value were reached, although it should be noted that 

 essentially these data are ephemeral,, The sound output of a 

 ship is directly dependent upon maintenance and may be affected 

 by the installation of new auxiliaries „ Slight injuries to a 

 propeller such as can be caused by a bit of driftwood may 



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