Popular Science Monthly 



807 



mmmmamm 



In order that a submerged submarine may direct its course accurately toward a hostile ship 

 it may be provided with microphones on its port and starboard bows. The difference in 

 the volume of sound received by the two microphones indicates the course to be pursued. 

 The sound can be converted into movements of a finger playing over a dial 



posed to the vibrations. At once 

 electrical circuits are closed and auto- 

 matic mechanism started which swings 

 the rudders of the torpedo and points 

 the nose of the torpedo toward its mark. 

 As soon as the microphones on both sides 

 are restored to electrical equilibrium, in 

 other words as soon as they hear with 

 equal clearness, the torpedo keeps on a 

 straightaway course. 



It is evident that the same principle 

 can be applied to submarine boats travel- 

 ing under water, with the difference that 

 since the submarine is manned by intel- 

 ligent human beings, the microphones 

 can be made merely to indicate the 

 course to be pursued, leaving to the 

 commander the task of steering a true 

 course. As in the case of the sound- 

 controlled torpedo, the submarine is 

 provided with microphones on its port 

 and starboard bows. Telephone ear- 

 pieces are provided which enable the sub- 

 marine commander to listen to the 

 sounds gathered by the microphones. 

 If the submarine is not pointed head on 



toward the ship to be destro\"ed the 

 microphone on the off side will hear less 

 than the other, and the difference in the 

 \olume of sound received by the two 

 microphone detectors will be noted at 

 once in the telephone receivers. The 

 commander changes his course until he 

 hears equally well with both ear-pieces. 



Seeing Sounds on a Dial 

 While it is perfectly feasible to direct 

 a submarine by telephone it is much 

 more effective to convert the microphone 

 vibrations into visual signals. As a 

 result the commander of a submarine 

 has only to watch a finger move over a 

 dial in order to know what course he 

 should steer. In a sense he sees the 

 sound which the microphone detectors 

 hear. The accompanying diagram sets 

 forth the essential principles of this 

 con\'ersion of the microphone vibrations 

 into visual signals so clearl>- that an 

 extended description seems hardly neces- 

 sary. 



While a visual steering indicator is 



