314 STUDIES IN PHYSIOLOGY 



A hard stroke, on the other hand, results in a loud note. 

 Hence, loudness depends on the amplitude of the vibrations. 

 A coarse violin string that vibrates but 50 to 100 times in 

 a second produces a very low tone ; when the number is 

 5000 to 10,000 per second, the note is high. The pitch of a 

 tone, then, depends on the frequency of vibrations. The 

 power of different individuals to distinguish tones varies 

 greatly. Some can hear a low note caused by as few as 30 

 vibrations per second, or a high note of 30,000 vibrations. 

 The movements of the wings of some insects is more rapid 

 even than this high rate ; hence, human beings cannot hear 

 the sounds they produce. 



With our eyes closed and at some distance from the in- 

 struments we can easily tell the difference between the 

 same note produced by a violin and a piano. This dif- 

 ference is not one of loudness, nor of pitch, but of quality. 

 When a violin or piano string gives forth a sound, the 

 string moves as a whole, and so produces what is called a 

 fundamental tone. At the same time different parts of the 

 string are vibrating more or less independently, and partial 

 or over tones are also produced. Hence, the air waves that 

 are set in motion by a violin string are a result of a funda- 

 mental tone combined with a certain number of overtones; the 

 piano string, on the other hand, while it can give out the 

 same fundamental, cannot produce the same combination of 

 overtones as does the violin. 



