the direction from which sounds arrive at their ears D Deter- 

 mination of direction through the binaural sense involved the 

 use of a dual listening system whether composed of simple 

 acoustic tubes or passages or„ as later developed, of elec- 

 trical devices and amplifiers It also required the exercise 

 of judgment by the operator as to the apparent location of the 

 sound he heard „ 



A second system of determining direction developed during 

 World War I was the MV (later called the multi-spot) array ^ 

 consisting of several receivers so connected that the signals 

 picked up by each would combine cumulatively only when the 

 sound came from a designated direction,, Sounds could be re- 

 ceived from an enemy submarine to the partial exclusion of the 

 extraneous noises originating in other directions c This prin- 

 ciple was of trememdous value in increasing the range at which 

 sounds could be heard Q 



Beginnings of Ec ho-Rangi ng , 



The multi-spot listening systems could detect a submarine , 

 but indicated only its direction and there was no way of deter- 

 mining the range from a single listening station It was not 

 until 1918 that the British set up a committee known as the 

 Allied Submarine Devices Investigation Committee (ASDIC) com- 

 posed of Naval experts and scientists of the Allied countries,, 

 It was largely through the work of this committee that atten- 

 tion was directed toward the determination of the range of a 

 sound source by echo-ranging 



Reduced to simplest terms' echo-ranging consists of using 

 an underwater sound projector to send out a sound beam and of 

 using an underwater sound receiver to listen for the echo sent 

 back when the outgoing sound strikes a reflecting surface „ 



Experiments with sub-surface echo-ranging had been con- 

 ducted as early as 1914 s when the Submarine Signal Company s 

 using Pessenden oscillators , had obtained echoes from the sea 

 bottom and from the submerged portions of icebergs „ Perhaps 

 the first echoes ever received from a submerged submarine 

 were observed by Boyle and his co-workers in England in 1918, 

 using a quartz oscillator developed as the result of pioneer- 

 ing work in piezoelectric research by the French physicist^, 

 Langevino By use of the Langevin oscillators it was possible 

 to transmit supersonic sounds under water. This method of 

 underwater sound transmission was further developed in Great 

 Britain by Rutherford and his associates. 



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