304 E. W. Scripture — Nature of Vowels. 



It seems clear that these vibrations represent the free vibra- 

 tions of the air in the mouth cavity aroused by a series of 

 sudden blows and that these sudden blows are due to explo- 

 sive openings of the vocal cords. In spite of this fact it seems 

 permissible to use the term " resonance vibrations " to include 

 these free vibrations of a cavity aroused by a blow as well as 

 the vibrations of a cavity impressed upon it by a source of 

 continuous vibration. 



The tone from the cords results from the succession of 

 strong vibrations that mark off groups. The period of the 

 tone from the vocal cords is represented by the distance from 

 the strong vibration at the beginning of each group to the 

 strong one at the beginning of the following group. 



The complexities of the small vibrations indicate the pres- 

 ence of several partial tones. These complexities change 

 steadily from the beginning of the vowel onward as the pitch 

 rises in a way to indicate the presence of at least the following 

 partials : 1, the fundamental cord tone consisting of a series of 

 explosions rising from a period of 0017 s (59, frequency) to 

 one of 0*0052 s (192, frequency) ; 2, a constant resonance tone 

 of 0*0034 s period (294, frequency) ; 3, a constant resonance 

 tone of 0*0013 s period (769, frequency) and 4, higher resonance- 

 tones undergoing change. 



The combined rise in pitch and in amplitude seen in the a is 

 found in all cases of I that have been examined. 



The minor complexities in the vibrations disappear at about 

 one-third of the distance from, the left on the second line in 

 the figure. At the same time the amplitude is strongly 

 increased. Shortly afterward the amplitude decreases and 

 finally reaches zero. Throughout the whole latter half the 

 curve has an entirely different character from that of the first 

 half; we are probably quite safe in considering it the curve of 

 i in the diphthong ai. Throughout the i the groups consist 

 of two vibrations, one slightly stronger than the other. The 

 period for a group 0*0052 s (192, frequency) remains constant till 

 near the end, where it lengthens to about 0*0122 s (82, frequency). 

 The resonance vibration forming half of each group remains 

 constant at -0026 s (384, frequency) through nearly all of the 

 i. Toward the close it still apparently remains at the same 

 period, producing phenomena of interference as the group 

 period is lengthened. The maintenance of pitch till near the 

 end, in spite of the fall in amplitude, occurs in all the cases of 

 /that have been examined. 



From the curve fori it seems justifiable to conclude that the 

 vocal cords emit explosions instead of sinusoid puffs of air 

 here as well as in the a. The explosion produces a strong free 

 vibration in the mouth cavity which is followed by another 



