PHONATION; ARTICUL'ATE SPEECH. 627 



which the air in the lungs and trachea is subjected was determined by Latour 

 to vary from 160 mm. of water for sounds of moderate, to 940 mm. of water 

 for sounds of highest intensity. With the escape of the air or the separation 

 of the vocal bands the vibration ceases and the sound dies away. 



The Characteristics of Vocal Sounds. In common with the sounds 

 produced by other music instruments, all vocal sounds are characterized 

 by intensity, pitch and quality, tone or color. 



The intensity or loudness of a sound depends on the extent or amplitude 

 of the to-and-fro vibration or the extent of the excursion of the vocal 

 band on either side of the position of equilibrium or rest; and this in turn 

 depends on the force with which the blast of air strikes the band. The more 

 forceful the blast of air, the larger, other things 

 being equal, will be the primary vibrations of 

 the bands, and hence the secondary vibrations 

 of the air in the upper air-passages. 



The pitch of the voice depends on the num- 

 ber of vibrations in a unit of time, a second. 

 This will be conditioned by the length of the 

 bands in vibration or the length and width of 

 the aperture through which the air passes and 

 the degree of tension to which the bands are sub- 

 jected. In the emission of sounds of highest FlG - 294. GLOTTIS SEEN 

 pitch the tension of the vocal bands and the 

 narrowing of the glottis attain their maximum. PITCHED SOUNDS, i, 2. Base 

 In the emission of sounds of lowest pitch the re- f the tongue. 3, 4. Epigiot- 

 verse conditions obtain. In passing from the ^noid^ar^ge^s. o^eni^g 

 lowest to the highest pitched sounds in the range between the true vocal cords. 

 of the voice peculiar to any one individual, 9- Aryteno-epigiottidean folds. 



, . -111 I0 - Cartilage of Santormi. n. 



there is a progressive increase in both the ten- Cuneiform cartilage. 12. Su- 

 sion of the vocal bands and the narrowing of perior vocal cords. 13. in- 

 the glottic aperture. In the production of low- 

 pitched notes of men, those due to vibrations lying between 80 and 240 per 

 second, the tension is regulated by the crico-thyroid muscle; the aperture of 

 the glottis during this time being elliptic in shape and relatively wide (Fig. 

 295). In the production of notes due to vibrations lying between 240 and 

 512 vibrations per second, the anterior fibers of the crico-thyroid muscle 

 relax and the thyro-arytenoid muscle comes into play; by its action the vocal 

 bands are more closely approximated and the vocal aperture reduced to a 

 linear slit. In the high-pitched notes emitted by soprano singers the vocal 

 bands are so closely applied to each other that only a very small portion in 

 front, bounding a small oval aperture, is capable of vibrating (Fig. 294). 

 The difference in the pitch of the voice in men and women is due largely to 

 the greater size and development of the vocal bands in the former than in the 

 latter. 



The quality of the voice, the timbre or tone-color, depends on the form 

 combined with the intensity and pitch of the vibration. As with sounds pro- 

 duced by music instruments, the primary or fundamental vibration of the 

 vocal band is complicated by the superposition of secondary or partial vibra- 

 tions (overtones). The form of the vibration will therefore be a resultant of 



