152 Dr. Gr. A. Campbell on 



the second hypothesis and those of the first, we refrain from 

 further detail. 



The second hypothesis has one advantage over the first. 

 There is no longer the same necessity to suppose c very 

 large compared with b. The equations resulting from c/b 

 finite are reasonably tractable. Hence our diagram includes 

 both saddles. 



University of Tasmania, 

 July 5, 1909. 



XII. Telephonic Intelligibility. By Geo. A. Campbell, Ph.D.* 



IN the August 1908 number (vol. xvi. p. 242) o£ the 

 ' Philosophical Magazine ' a paper by Lord Bayleigh 

 contains some notes upon the acousticon, in the course o£ 

 which he says : — 



" The reproduction of speech, given at about one foot 

 away from the microphone, was better than anything I had 

 ever heard before. The first impression was that all the 

 consonantal sounds were completely rendered, but this turned 

 out to be an illusion. In listening to the numerals, given in 

 order, the observer would feel confident that he heard the/ in 

 Jive and the 5 in six. But if the initial sound was prolonged 

 — fffi ve i s s s ' lx i ^ ne observer could not tell until he heard 

 the sequel which it was going to be. Further, if the sounds 

 were given as n ive,ffix, they were heard normally as five 

 and six. It was plain that there was no difference in the 

 rendering of f and s. I am informed that this is a well- 

 known difficulty in ordinary telephoning, and that in spelling 

 a name containing f or s it is usual to say '/ for Friday ' or 

 1 s for Saturday.' But the articulation of the acousticon is 

 so superior that it was surprising to find the failure complete. 

 The characterization of sh was not much better, though after 

 a little practice I could distinguish it from ,9 or/', but pro- 

 bably only by a greater loudness. 



" These failures might have been ascribed to my rather 

 defective hearing, but other observers with normal hearing- 

 did no better." 



This statement of telephonic intelligibility is typical of the 

 impression made by the general use of the telephone. Most 

 of us feel that we understand almost everything transmitted 

 by the telephone or next to nothing, according as we are 

 listening to a familiar voice talking upon some well-known 

 subject, or as we are obliged to listen to disconnected syllables 

 spoken possibly in a strange tone of voice. This is obviously 

 a case for the statistical analysis of results. 



Some time ago the American Telephone and Telegraph 



* Communicated by the Author. 



