VOICE AND SPEECH 525 



the vibrations of the cord are apparently confined to their inner margins 

 the aperture of the glottis is wider in front than behind, so that more air 

 escapes during phonation by this method than in the production of the 

 chest voice. 



In order to change the pitch of the note the following means are probably 

 employed in the larynx : 



(1) Alteration in the tension of the vocal cords. 



(2) Alteration in the length of the part of the vocal cords which is 

 free to vibrate, which can be accomplished by the approximation of the 

 arytenoid cartilages to one another, or by their approximation to the thyroid 

 cartilage. 



(3) The alteration in the shape of the vocal cords, which is determined by 

 the activity of the different portions of the internal thy ro- arytenoid muscles. 



(4) The varying pressure of the blast of air passing through the 

 glottis. 



The loudness of the tone produced is practically proportional to the 

 force of the blast of air employed. The quality or timbre of the voice 

 depends not so much on the vocal cords as on the accessory resonating 

 apparatus, represented by the trachea and chest and by the cavity of the 

 mouth. The greater part of the education involved in voice training is 

 directed to the modification of the shape of the mouth cavity, so as to 

 secure the greatest possible fulness, i.e. richness in overtones, of the tone 

 produced in the larynx. 



THE MECHANISM OF SPEECH 



The sounds employed in speech, viz. vowels and consonants, are produced 

 by modifying the laryngeal tones by changes in the shape of the mouth and 

 nasal cavities. In whispering speech there is no phonation at all, but the 

 sound is produced by the issue of a blast of air through a narrow opening 

 between the lips, between the tongue and soft palate, or between the tongue 

 and the teeth. 



The vowel sounds are continuous, whereas the consonants are produced 

 by interruptions, more or less complete, of the outflowing air in different 

 situations. The vowel sounds, u, o, a, e, i (pronounced oo, oh, ah, eh, ee), 

 are tones, i.e. are produced by a regular series of vibrations. These tones 

 take their origin in the mouth cavity, as can be shown easily by the fact 

 that we can whisper these sounds distinctly without any phonation what- 

 ever. To each of them corresponds one or two distinct notes, the pitch, i.e. 

 the resonance, of which is regulated by the shape of the cavity in which 

 they are produced. It is possible to determine these notes by means of 

 resonators. The pronunciation even of the simplest vowel sounds differs 

 in different individuals. For instance, those pronounced by a Londoner 

 differ from those pronounced by a man from Manchester or from Yorkshire, 

 and the French vowels differ somewhat in pitch from those employed 

 by the German, and these again from those employed by the average English- 

 man. 



