VOICE 175 



walls are made up of cartilages, together with various muscles 

 and membranes. Across the cavity in an anteroposterior 

 direction are stretched the vocal cords, by the vibration of which 

 the voice is produced. Mere vibration of the cords held in 

 a state of tension by muscular action produces in itself but 

 a feeble sound. This is intensified by reenforcement of the 

 vibrations by resonating cavities above and below the cords. 

 It is necessary to consider three features of the voice the 

 intensity, the pitch, and the quality. The intensity depends 

 upon the amplitude of vibrations of the cords. This is partly 

 the result of their structure and partly of the energy with which 

 the air passes between them. The pitch is determined by the 

 thickness, tension, and length of the cords. The quality of 

 the tone depends upon the character of the upper partial 

 tones which are combined with the fundamental tone. These 

 are varied by altering the shape and size of the buccal and 

 nasal cavities. The voice is controlled by an exceedingly 

 complex nervous mechanism of afferent and efferent fibers to 

 various centres in the cerebral cortex. That relations between 

 the hearing and speech centres, for instance, are very intimate 

 is shown by the fact that dumbness is usually a defect of hear- 

 ing which leaves the voice uncontrolled by the ear in pitch 

 and quality. The pitch of the voice is elevated usually by 

 the contraction of the cricothyroid muscle, which stretches 

 the vocal cords. There are numerous other methods of alter- 

 ing the pitch. Whenever there is a transition from one method 

 to another, a break occurs in the musical scale. The range 

 of voice between these breaks is known as a register. The 

 lowest register is commonly designated as the chest voice, and 

 the highest as the head voice. When a third division is made, 

 it is by some called the falsetto. Speaking consists of short 

 musical sounds produced by the vocal cords with other noises 

 added by the mouth parts, the whole being interrupted by 

 different methods of obstruction. In whispering the musical 

 component is greatly replaced by noisy vibrations. 



