104 SOUND 



source of a sound by noting its pitch. The vibrations 

 of a small body are generally more rapid than in a larger 

 body of the same sort, and the sound produced has a 

 higher pitch. 



119. Limiting Pitch. Some waves are too long and 

 some too short to affect the ear ( 104). The limits within 

 which waves may cause sound vary in different persons. 

 Few can hear sounds lower than twenty vibrations per 

 second, or higher than thirty thousand per second. 



In music, middle C (C natural) has 264 vibrations per 

 second; the octave above (high C) has twice as many 

 (528), and the octave below has one half the number 

 (132). A man's voice can rarely make a tone lower 

 than 150 waves per second; while children may, in 

 screaming, reach a pitch of several thousand vibrations. 



120. Quality. The first two features of sounds, 

 pitch and loudness, are common in our experience and 

 not hard to understand ; the third, quality, may need a 

 bit of thought. A piano and a violin may sound the 

 same tone ; it has the same pitch in each case, and may 

 be sounded with equal loudness, yet we should have no 

 trouble at all in telling the sound of a violin from that 

 of a piano. The same would be true of tones made by a 

 cornet, banjo, harmonica, harp, flute, or other instrument. 

 Clearly there is some feature of tones, other than loud- 

 ness or pitch, which seems to depend upon the instru- 

 ment that produces them ; this feature is called quality. 



121. Quality explained. Very few sounds are pure 

 tones ( 114, 115); even those which are pleasing 

 enough to be called musical contain a few weaker tones 



