SOUND 171 



12. When a comb is drawn rapidly across the edge of a card, would 

 you consider the sound produced a musical sound or only noise? 



13. Suppose the card held on the rim of a rapidly revolving and regu- 

 larly notched wheel. Would you call the sound music or noise? 



14. Why do the wings of a bee make a musical note when the wings 

 of a bird in flight do not? 



15. Of what use is the reed or thin flap of metal in a harmonica or 

 mouth organ? 



16. How does placing the Jew's-harp in front of the mouth make it 

 sound louder? 



17. Stretch a string across two supports in such a way that it is free 

 to vibrate. When does it give out the higher note, when it is loosely or 

 tightly stretched? 



18. When does it vibrate most rapidly? 



19. Using the finger for a support, cause different lengths of the string 

 to vibrate. Which gives off the higher note, a short or a long string? 



20. Is the foregoing true of pianos, harps, and violins? 



21. Explain the humming of telegraph and telephone wires. 



22. What produces the sounds in an aeolian harp? 



23. Which would you expect to give the higher note, a large or a small 

 tuning fork? 



24. Suppose the wheel mentioned in question 13 to have its speed 

 suddenly increased. What effect would this have on the tone produced? 



