736 VOICE AND SPEECH. [CH. LTV. 



resonating cavities, which by alterations in their shape and 

 size, are able to pick out and emphasize certain component 

 parts of the fundamental tones produced in the larynx. The 

 natural voice is often called the chest voice. The falsetto voice is 

 differently explained by different observers ; on laryngoscopic 

 examination, the glottis is found to be widely open, so that there 

 is an absence of chest resonance ; some have supposed that the 

 attachment of the thyro-arytenoid muscle to the vocal cord 

 renders it capable of acting like the finger on a violin string, 

 part of the cord being allowed to vibrate while the rest is held 



still. Such a shortening of a 

 vibrating string would produce 

 a higher pitched note than is 

 natural. 



Musical sounds differ from one 

 another in three ways : 



i . In pitch. This depends on 

 the rate of vibration ; and in the 

 Fig- 557. View of the upper part of the case of a string, the pitch in- 



lary nx as seen by means of the laryn- , i j 



goscope during the utterance of a CreassCS With the tension, and 



diminishes with the lenth of 



arytenoid cartilages ; z, base of the the String. The VOCal COrds of 

 tongue ; ph, the posterior wall of the 



pharynx. (Czermak.) a woman are shorter than those 



of a man,, hence the higher 



pitched voice of women. The average length of the female cord 

 is 1 1 '5 millimetres; this can be stretched to 14; the male cord 

 averages 15-5 and can be stretched to 19-5 millimetres. 



2. In loudness. This depends on the amplitude of the vibra- 

 tions, and is increased by the force of the expiratory blast which 

 sets the cords in motion. 



3. In " timbre." This is the difference of character which 

 distinguishes one voice, or one musical instrument, from another. 

 It is due to admixture of the primary vibrations with secondary 

 vibrations or overtones. If one takes a tracing of a tuning-fork 

 on a revolving cylinder, it writes a simple series of up and down 

 waves corresponding in rate to the note of the fork. Other 

 musical instruments do not lend themselves to this form of 

 graphic record, but their vibrations can be rendered visible by 

 allowing them to act on a small sensitive gas-flame ; this bobs 

 up and down, and if the reflection of this flame is allowed to fall 

 on a series of mirrors, the top of the continuous image formed is 

 seen to present waves. The mirrors are usually arranged on the 

 four lateral sides of a cube which is rapidly rotated. If one 

 sings a note on to the membrane in the side of the gas-chamber 



