The physical nature of sound waves





Fred's little brother Bobby is a real pain in the neck. He is always talking -- about baseball, comic books, Egyptian antiquities, flavors of ice cream -- he just won't be quiet. Fred decides to make the best of a bad situation: he builds a device to harness the power of Bobby's voice. A very thin panel 1 meter on a side converts the energy of the sound waves coming out of Bobby's mouth into electricity.



     Q:  Assume that Bobby talks at an ordinary
         volume, so the sound waves have a pressure
         amplitude of 2.5 x 10^(-2) pascals. 
         Estimate the power this device will
         produce.  

  
     Q:  Could it light an ordinary bulb?


     Q:  Fred builds a solar panel which is also
         1 meter on a side and places it outside
         on a sunny day.  Roughly how much 
         power does this panel produce?