THE HOMEMADE ORCHESTRA 335 



from C to C are all equal, and we have become more or less accus- 

 tomed to the little discrepancies this involves so that we scarcely 

 notice them. 



When a taut string is made to vibrate by bowing it and at the 

 same time it is lightly touched at its mid-point, it may then 

 vibrate not only as a whole, but in each half also (Fig. 172). 

 The note emitted by the vibrating halves is of course an octave 

 higher than the note emitted by the whole string. Again, if 

 the string is similarly touched at a point one-third of the distance 

 from one end to the other, it vibrates in segments as well as in 

 its entirety and other notes are emitted in addition to the funda- 

 mental one. Such tones are known as overtones, and in most 

 musical instruments the quality of the sound emitted is due 

 quite as much to the number and character of the overtones 



FIG. 172. String vibrating as a whole and in halves 



and to the resonance as to the vibration of the string or air 

 column that sets the sound going. 



So the pitch of a note is determined by the rate of vibration 

 of the body that originates it or by the wave-length, since this 

 is determined by the former factor. The intensity of the note 

 is determined by the amplitude of vibration of the particles 

 of the body from which the sound comes. The greater the 

 amplitude, the louder the sound. The quality of the sound 

 depends on the overtones. 



The human voice is produced by the vibration of two mem- 

 branous flaps that lie on either side of the larynx or voice box, 

 a cartilaginous structure at the top of the windpipe, felt in the 

 neck as the Adam's apple (Fig. 173). In ordinary respiration 

 these flaps are drawn to one side and lie loose. When one desires 

 to speak, they are drawn nearly together and rendered taut, so 



