30f46597   
   XPost: sci.physics.acoustics, sci.physics   
   From: kludge@panix.com   
      
   RichD   wrote:   
   >   
   >This is what I don't get.   
   >How do you get a reflection from the open end?   
   >I can't picture that.  It doesn't jibe with my (fading)   
   >memory of studying transmission lines, in EM,   
   >where you get standing waves, with a termination   
   >at each end.   
      
   No, you DON'T get standing waves with a termination at each end.   
      
   If you short the end of the cable, you get an inverted reflection back.   
   If you leave the end of the cable open, you get a non-inverted reflection   
   back.   
      
   ONLY if the cable is terminated into an impedance equal to the characteristic   
   impedance of the line do you not get a reflection; the termination load   
   appears like additional cable and the signal goes quietly into it as if it   
   were so.   
      
   The same thing happens with an open or closed organ pipe and creates the   
   internal resonance of the pipe.   
      
   In a trumpet it gets interesting.... because the bell of a trumpet is   
   effectively an impedance-matching transformer....   
   --scott   
   --   
   "C'est un Nagra. C'est suisse, et tres, tres precis."   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)