632 



BELL SYSTEM TECHNICAL JOURNAL 



Stress 



Since our observations have sliown qualitatively that the louder 

 syllables ha\e the greater rise of mean power, means are available for 

 calibrating the stress modulation of the voices under test. To form a 

 discriminant for each speaker we proceed in the following way: 



(1) 

 (2) 



(3) 



(4) 



Measure the Pm of each syllable; 



F"ind the ratio of each Pm to the greatest Pm occurring in the 

 speech; call this ratio e; 



Find the proportional number, s/j, of syllables for which t is 

 greater than the magnitude n, where n nia\' vary between 

 Oandl; 



Plot the variables s,^ and n against each other to give the re- 

 quired curve. 



Enehgy Stkess 

 l-'ig. 2a — Composite stress curves of 16 voices 



The analogous relation between s\llal)ic energy and stress is found 

 by using the total energy of eacli syllable instead of Pm in the above. 



A large number of these curves has been so obtained, but it will 

 suffice to consider here a few of the representative types. F"ig. 2a 



