ECHOES AS MESSENGERS 



Fig. 4. Sound does not cast sharp shadows, but it does 

 go around corners as well as being reflected back from 

 solid objects. 



placed between the sound source and the listener's ear. 

 Sound goes around comers more easily, and conse- 

 quently it is more difi&cult to exclude it from a house or 

 room or from a piece of scientific apparatus (Fig. 4). 

 Even though sounds can be reduced in loudness by walls 

 and other barriers, we seldom think about the degree to 

 which they are blocked, transmitted, or reflected. So un- 



43 



