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Common Science 



FIG. 102. When the wave reaches the end of the sink, it is reflected back. 

 Sound waves are reflected in the same way. 



to the other so rapidly that no distinct echo is heard, 

 and there is merely a confusion of sound. 



When you drop a pebble in water, the ripples spread 

 in all directions. In the same way, when you make a 

 sound in the open air, the air waves spread in all direc- 

 tions. But when you shout through a megaphone the 

 air waves are all concentrated in one direction and conse- 

 quently they are much stronger in that direction. How- 

 ever, while the megaphone intensifies sound, the echoing 

 from the sides of the megaphone makes the sound lose 

 some of its distinctness. 



Why it is hard to understand a speaker in an empty 

 hall. A speaker can be heard much more easily in a 

 room full of people than in an empty hall. The sound 

 does not reflect well from the soft clothes of the audience 



