214 ADVANCED PHYSIOLOGY 



enlarge, and he goes through an experience called a "change 

 of voice"; at the close of this period the larynx assumes its 

 permanent shape and size, and the voice remains practically 

 the same thereafter. 



Quality of Voice. The difference in the " sound " of the 

 voice in different people is due to the shape and size of various 

 air spaces associated with the throat, mouth and nose. The 

 strings taken from the finest violin in the world and stretched 

 from one nail to another in a board would not give out pleas- 

 ing sound, however they were bowed. In like manner, air in 

 a barrel changes the " sound " of the natural voice when one 

 speaks into it; speaking into bottles of different sizes gives 

 rise to different sounds. The fine tone of an instrument is 

 due more to the vibration of the air inside it than to the 

 strings themselves. 



In the same way the character of the voice is largely de- 

 termined by certain air spaces; by the columns of air in 

 the trachea, in the pharynx and in the nasal passages; by 

 certain air cavities in the bones between the pharynx and 

 the brain, and by others in the bones making up the parti- 

 tion between the nasal passages and the brain; Fig. 96. 



These spaces are all of much consequence in determining the 

 finer characteristics of the singing voice, and much of voice 

 training consists in developing the habit of "placing" the voice 

 in such a way as to obtain the best use of these air chambers. 



Loudness of Voice. The loudness of the voice is due to 

 the amount of air and the force with which it is driven through 

 the slit between the vocal cords. A piano string which is set 

 in vibration by a very forcible stroke gives out a loud sound; 

 struck lightly, the same string, vibrating through lesser dis- 

 tances, gives out a fainter sound though of the same pitch. 

 In a similar way, the loudness of the voice depends upon the 

 amount of the vibration of the vocal cords, which in turn is 

 determined by the strength of the air current. 



Pronunciation is effected almost entirely by the shaping of 



