8 



The Production of Sounds 



Dveryc 

 lona: i 



^G THE Second World War, the United States was naturally 

 y concerned about the possibility of submarine attacks on her 

 and vulnerable coastline, and so set up a protective sofar 

 barrier to give warning of an enemy approach. Submarines might be 

 invisible, but sofar made them audible, as guards with hydrophones glued 

 to their ears listened for suspicious sounds. 



In 1942, almost a year after Pearl Harbour, a young sofar operator 

 suddenly heard his hydrophone emit a mysterious creaking noise, and saw 

 the hands on the dials of his instruments swinging ominously. The alarm 

 was sounded and naval aircraft and a patrol boat set out to investigate. 

 However, before they could go into action, the instruments had ceased to 

 register the disturbance and it was assumed that the submarine had 

 escaped. A routine report was sent to the Navy Department in Washington 

 and the incident promptly forgotten. 



But not by Washington, for there similar reports poured in in alarming 

 numbers. It looked as if enemy submarines could infest U.S. coastal 

 waters without anyone being able to do anything about it. Moreover, 

 coastal patrol vessels off the Aleutians continually reported sounds like 

 those of a ship's screws, or continuous clicking noises of unidentifiable 

 origin. Similar reports came from the Solomon Islands, and there was the 

 strange episode of a mine going off without a ship having been anywhere 

 near it. The Navy Department was greatly perturbed until somebody 

 suggested that the noises might not be caused by enemy naval detachments 

 at all but by fish, perhaps by dolphins. 



This explanation seemed fantastic because fishes had for centuries been 

 thought to be mute. Thus in his ode to Melponeme, Horace wrote: 'O 

 mutis quoque piscibus.' To solve the problem, zoologists were called in 

 and asked what they knew about the subject. Unfortunately their know- 

 ledge was very scanty. They could quote Aristotle's (350 b.c.) saying that a 

 captured dolphin squeaks and moans above the water, there were some 



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