THE SOUNDS OF THE VOCAL APPARATUS. 609 



CONDITIONS INFLUENCING THE SOUNDS OF THE VOCAL 



APPARATUS. 



The pitch of the voice-tone depends upon the following factors: 



1. The tension of the vocal bands; hence upon the degree of contrac- 

 tion of the crico-thyroid and posterior crico-arytenoid muscles, with the 

 assistance of the vocal or internal thyro-arytenoid muscles. 



2. The length of the vocal bands. In this connection it should be 

 noted: (a) That children and women, with shorter vocal bands, pro- 

 duce higher tones. The voices of women are about one octave higher 

 than those of men. (b) If the arytenoid cartilages are pressed tightly 

 together by the action of the transverse and oblique posterior arytenoid 

 muscles, so that only the vocal bands themselves can vibrate, while the 

 intercartilaginous parts between the vocal processes cannot, then the 

 tone will be higher. To produce deeper tones, the vocal bands, and also 

 the margins of the arytenoid cartilages, must vibrate. At the same 

 time the space above the exit of the larynx enlarges, so that the throat 

 becomes more prominent, (c) Each individual has a certain medium 

 pitch of voice, which corresponds to the least possible muscular tension 

 within the larynx. 



3. The strength of the blast. That the strength of the blast is able 

 to raise the pitch of the tone in the human larynx is shown by the fact 

 that the highest tones can be emitted only in a loud voice. With 

 medium tones the air-tension in the trachea amounts to 160 mm., with 

 high tones to 200 mm., with exceedingly high notes to 945 mm., in 

 whispering only to 30 mm. of water measured through a tracheal fistula. 

 In changing the intensity of a tone from loud to soft, or conversely, 

 while maintaining the same note, the muscular action must undergo 

 a change in force. When the note is loud the force diminishes, while 

 it increases as the tone becomes soft. J. Muller called this process the 

 "compensation of energy in the larynx." 



The following accessory phenomena have been observed in the production of 

 high notes, but no certain interpretation of them has been given: (a) As the pitch 

 of the note increases, the larynx becomes elevated, partly because the elevating 

 muscles of the larynx are brought into activity, and partly because the intra- 

 tracheal air-pressure lengthens the trachea to such an extent that the larynx is 

 raised up. The uvula also is raised higher and higher. (6) The upper vocal 

 bands approach each other more and more, without touching or participating in 

 the vibrations, (c) The epiglottis inclines more and more backward over the 

 glottis. In explanation of c and b it is supposed that, in the production of high 

 tones, all of those muscles are active that aid in shortening the vibrating section 

 of the rim of the glottis and in constricting its opening. In this act the edge of 

 the (external) thyro-arytenoid muscle displaces the upper vocal band inward; 

 while the epiglottis is drawn downward by those fibers that pass upward toward 

 it laterally the thyro-ary-epiglottic muscle. 



4. So-called registers can be distinguished in the voice. There is 

 generally the chest-register, the thorax vibrating (pectoral fremitus), 

 and the voice appearing to come from the depths of the chest ; and also 

 the head-register, the voice apparently coming from the throat. The 

 latter, with its soft timbre and lack of resonance in the air-tube, is 

 designated also a falsetto voice or shriek. Oertel observed under such 

 circumstances that the vocal bands vibrated so as to form nodal lines 

 across their width; at times only one nodal line is formed, so that the 

 free border of the vocal band and the basal border vibrate, and are sepa- 

 rated from each other by a nodal line parallel to the edge of the vocal 



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