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BELL SYSTEM TECHNICAL JOURNAL 



arises, "How much energy would be involved?" It is not possible 

 here to describe the devices by which we were able to measure accu- 

 rately the energies and frequencies involved in speech, but the results 

 of this research work are interesting. When this sentence is spoken 

 fairly rapidly, it will contain about two hundred ergs of energy. 

 About 500,000,000 ergs of energy pass through the filament of an 

 ordinary incandescent lamp each second. This shows that the acoustic 



;!: -3.00 



o 



o 



?-3.25 



I 

 u 

 t-3.50 



Q. 



-3.75 



Fig- ^ — Graph of the loudness of the various sound elements when the sentence 

 "Joe took Father's shoe bench out " is spoken. 



energy in this sentence is very small. Putting it in another way, it 

 would require five hundred persons speaking this sentence continuously 

 for a year to produce sufficient speech energy to heat a cup of tea. 



An examination of the wave produced by this sentence shows that 

 the vowels contain considerably more energy than the consonants. 

 Exact measurements have indicated that in ordinary conversation the 

 ratio of the intensity of the faintest speech sound, which is th as in 

 "thin," to the loudest sound, which is aw as in "awl," is about one 



