U. S. NAVY MV TYPE OF HYDROPHONE AS AN AID 

 AND SAFEGUARD TO NAVIGATION. 



By H. C. HAYES, Ph.D., 

 Physicist, Sound, U. S. Navy. 



(Read April 24, 1920.) 



Summary. 



The experimental work in connection with hydrophone develop- 

 ment, which the United States Navy has carried out during the past 

 year, has demonstrated that the MV type of hydrophone can effec- 

 tively aid and safeguard navigation in the following ways : 



1. By hearing and locating a moving propeller-driven vessel at 



ranges varying from 2 to 10 miles, depending upon the amount 

 of noise which the vessel makes and providing the depth is 

 within 100 fathoms. 



2. By accurately determining the direction of submarine sound sig- 



nals, located at fixed points along the coast and at harbor en- 

 trances, at various ranges up to 30 miles, depending upon the 

 amount of local or water noises encountered. 



3. By giving a continuous sounding record while underway at any 



speed for depths less than about three times the length of the 

 vessel. 



4. By hearing, locating, and giving the course of any vessel equipped 



with a suitable submarine sound signal at ranges up to 30 

 miles. 



5. By affording a means of exchanging code messages between ves- 



sels equipped with the proper apparatus up to ranges of 20 



miles in water of any depth, thus giving an auxiliary to the 



radio. 



The results of the various tests that have thus far been carried 



out indicate that this type of hydrophone will prove capable of 



further aiding and safeguarding navigation in the following ways : 



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