XPost: sci.physics   
   From: nobody@but.us.chickens   
      
   On 12/9/2010 9:51 AM Dick Pierce spake thus:   
      
   > The MORE interesting question is when you DO push aire   
   > through some instruments, like the flute or recorder or   
   > pipe organ, how does THAT work.   
   >   
   > Well, in a somewhat analogous fashion. These instruments   
   > all depend upon producing a thin sheet of air, which has   
   > some turbulenace in it. The chaotic nature of the resulting   
   > flow might initially flow more into the tube than out and   
   > thus slightly pressurizing. That pressure wave travels to   
   > the end of the tube (at the speed of sound, not surprisingly)   
   > and, whethet the tube is open or closed, some of it is   
   > reflected back down and when it gets to the point where it   
   > started (the "mouth"), it opos the sheet out, thich sends a   
   > slight evacuation wave on the same trip. The round-trip time   
   > is largely dependent on the length of the tube, so the the   
   > longer the tube, the less frequent the flip-slop occurs, and   
   > the lower the note: the shorter the tube, the quicker the   
   > round-trip time, the faster the flip-flop, and the higher   
   > note.   
      
   I'd always understood that wind instruments like flutes and recorders   
   work because the airstream gets split (by the fipple in the recorder).   
   But I still have no idea how this produces oscillation. Very mysterious.   
      
   You mentioned the complex waveform produced by a vibrating reed. Maybe   
   similar to bowed instruments like the violin, in which the sound   
   generator (a sticky bow repeatedly "grabbing" and releasing the string)   
   produces roughly a triangular wave. (Dunno what the waveform of the   
   sound that emerges from a violin actually looks like, though; presumably   
   the body of the instrument does some wave-shaping.)   
      
      
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