318 STUDIES IN PHYSIOLOGY 



vowels are a, e, i, o, and u, and these different sounds are 

 produced by altering the shape of the mouth cavity through 

 movements of the lips and cheeks. In none of these 

 sounds does the tip of the tongue touch the palate, the 

 teeth, or the lips. Many of the consonants, on the other 

 hand, are pronounced when the tongue is moved against cer- 

 tain regions of the walls of the mouth. Thus, when we 

 utter t, d, th, or n, the tongue tip presses against the front 

 teeth and hard palate ; these consonants are, therefore, 

 called lin'gu-als (Latin lingua = tongue). In articulating 5, 

 p, and ra we press the lips together, and for this reason 

 we speak of these consonants as la'bi-als (Latin labium = 



HP). 



Loudness, Pitch, and Quality. The loudness of the voice 

 depends upon the force with which the vocal cords and the 

 resonating air columns are made to vibrate. In whispering, 

 faint noises are produced by the escaping air as it is forced 

 through the glottis and mouth opening. The vocal cords do 

 not vibrate when we whisper. 



When a high note or tone is produced, the vocal cords are 

 stretched tightly and made to vibrate rapidly. Hence, as is 

 the case in other instruments, the pitch of the voice corre- 

 sponds to the rapidity of the vibrations. If we feel of the 

 larynx when uttering a high note, we become conscious that 

 it has risen a little toward the throat. By this means the 

 resonating chamber becomes shorter, and so its rate of 

 vibration can be quickened by the air which is forced from 

 the lungs. In early life the resonating chambers and the 

 larynx are smaller, and the vocal cords are shorter than in 

 later years ; for these reasons the pitch of a child's voice 

 is higher. During the period from thirteen to sixteen years, 

 especially in boys, the rate of growth in this region of the 

 body is very rapid, and so, after "the voice has changed," 

 its tone becomes deeper. 



The distinguishing quality of an individual voice depends 

 on the combinations of fundamentals and overtones. While 



