TRANSATLANTIC TELEPHONING. 



301 



these various transformations all the distinctive characteristics of the 

 sound must be preserved. The vibrations of the transmitter disk, the 

 electric waves that traverse the wire, the vibrations produced in the 

 receiver disk, must retain all the elements that characterized the origi- 

 nal vocal sounds. This must be, or we could not, as we do, recognize 

 not onl}^ the spoken words, but the tone and modulations of the voice, 

 and even the mood of the speaker. The imperfections of electrical 

 conductors not only tend to enfeeble, but to distort the electric waves, 

 and a little distortion is sufficient to change the character of the sound 

 as it is reproduced, and render it unrecognizable. What is meant by a 

 distorted wave may be seen from lig. 1, where a may i-epresent a 

 wave as given to a telephone line, and i, c, d the same wave which has 

 become distorted by a change in the relation of its elements during 

 transmission; d would hardly be recognized as having an}- thing in 

 common with a. 



Fig. 1. 



Let us consider a little further the effect of the conducting line 

 upon the waves that transmit speech. Speak the words ''soap" and 

 "soup," "mine" and "mean." How do you make the distinction? 

 By a little more or less opening of the mouth, and a little more or less 

 pursing of the lips. Helmholtz has shown us in what respect the 

 corresponding sound waves differ. It appears that it is only in the 

 little waves superimposed upon the main wave, in the little ripples, 

 so to speak, on the surface of the larger wave. The wave for the 

 "ou" in "soup" might look like this: 



And the w^ave for the " o" in " soap," like this: 



Fig. 3. 



