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68o TEXT-BOOK OF PHYSIOLOGY 



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- 

 Fir,. 279. GLOTTIS SEEN jected. In the emission of sounds of highest 

 WITH THE LARYNGOSCOPE DUR- pitch the ten sion of the vocal bands and the 

 ING THE EMISSION OF HIGH- r . , , . . , . 



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

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

 */<?"& O 7 peng * conditions obtain In passing from the 

 between the true vocal cords, lowest to the highest pitched sounds m the range 

 9 . Aryteno-epigiottidean folds. o f t h e voice peculiar to any one individual, 

 cuneWo r rm ge ca ^:gr n T, Sul there is a progressive increase in both the ten- 

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



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. 

 283). 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. 279). 

 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 musical 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 

 the blending of a number of different vibrations. The quality of the sound 

 produced in the larynx is, however, modified by the resonance of the mouth 

 and nasal cavities; certain of the overtones being reinforced by changes in 

 the shape of the mouth cavity more especially, thus giving to the voice a 

 somewhat different quality. 



The Varieties of Voice. The region of the music scale, comprising 

 all vibrations between 32 and 2048 per second, with which laryngeal sounds 

 are in accord will vary in the two sexes and in different individuals of the 



