Sound 



187 



strike it. Now pour half 

 tlie water out, and strike 

 the glass again. Do you 

 get the higher sound when 

 the column of water is 

 shorter or when it is 

 longer ? Stretch a rubber 

 band across your thumb 

 and forefinger. Pick the 

 band as you make it 

 tighter, not making it 

 longer, but pulling it 

 tighter with your other 

 fingers. Does it make a 

 higher or a lower sound 

 as you increase the tight- 

 ness? Stretch the band 

 from your thumb to your 

 little finger and pick it; 

 now put your middle 

 finger under the band so 



as to divide it in halves, and pick it again. Does a short 

 strand give a higher or lower pitch than a long strand ? 



A violinist tunes his violin by tightening the strings ; 

 the tighter they are and the thinner they are, the higher 

 the note they give. Some of the strings are naturally 

 higher than others ; the highest is a smaller, finer string 

 than the lowest. When the violinist plays, he shortens 

 the strings by holding them down with his fingers, and 

 the shorter he makes them the higher the note. A bass 

 drum is much larger than a high-pitched kettledrum. 

 The pipes of an organ are long and large for the low 

 notes, shorter and smaller for the high ones. 



FIG. 103. When the prongs of the tuning 

 fork are made longer or shorter, the pitch 

 of the sound is changed. 



