392 VOICE AND SPEECH. 



louder until a certain length is reached, after which it grows 

 weaker. Forks of different length will be found to have their 

 own length of air-column, respectively, which reinforces its sound. 

 The explanation is this : u When the prong a moves to 6, it makes 

 half a vibration, and hence generates half a sound-wave. The 

 condensation it produces passes down the tube AB, is reflected 

 from the bottom, and returns to unite with other waves sent out 

 by the prong. Now, if AB is of the proper length, this condensa- 

 tion can move up the tube and return to combine with the con- 

 densation produced by the prong moving from b to a, thus making 

 the condensation more marked and thereby strengthening the 

 sound. The effect of the fork on the column of air is to set it 

 in vibration, and the layer of air at its mouth has the sound-pro- 

 ducing properties of a sonorous body of large area" (Carhart and 

 Chute). 



As already stated, the voice is produced by the vibrations of 

 the tense vocal cords due to the expiratory blast of air emitted 

 from the lungs. As in musical sounds, so in the voice, the three 

 properties of intensity, pitch, and quality are to be found. 



Intensity. The intensity or loudness of the voice depends 

 upon the amplitude of the vibrations of the b'ands, the force with 

 which the air is emitted, and the resonance cavities, viz., the 

 chest and the cavities of the head, all of which contain air. The 

 air being set in sympathetic vibration by the vibrations of the 

 vocal bands, reinforces the sound produced by the bands. 



Pitch. The pitch of the tones produced by the vibrating 

 vocal bands depends upon the same elements as in any vibrating 

 string i. e., length, tension, and thickness. Thus, the female 

 voice is of a higher pitch than the male, because of the lesser 

 length of the bands in the female than in the male. 



The following table (Browne and Behnke) shows the vibrational 

 number of a few extreme tones used in music : 



Large organs C iv. . . 16| vibrations per 



Latest grand pianos A iv. . . 27^ 



Ordinary modern pianos .... C iii. .. 33 



Double bass E iii. . . 41^ 



Pianos with usual compass ... A iii. . . 3520 



" u exceptional compass. C iv. . . 4224 



Piccolo-flute D iv. . . 4752 



The length of the bands in childhood is from 6 to 8 mm. ; in 

 the female adult about 11 mm., and may be stretched to 15 mm. 

 or more ; and in the male adult 15 mm., with a capability of ex- 

 tension to 20 mm. When the cricothyroid muscle contracts, the 

 bands are lengthened and made tense. The structures of the bands 

 and their attachments are such that they may vibrate as a whole or 

 only in part ; thus, when the vocal processes of the arytenoids are 

 approximated, as they are by the contraction of the lateral crico- 



