clipka <ano### [at] anonymousorg> wrote:
> Strictly speaking, with pressure there's only "push", with "pull" being 
> actually a push in the opposite direction:

  The "push" and the "pull" are differentiated by the direction in which
the effect propagates. Also a "push" is a higher pressure wave which moves
towards some directin, while a "pull" is a lower pressure wave which moves
in that same direction.

  This can be visualized by imagining a long string of small spheres, each
sphere being connected to the next with a spring. If you push the first
sphere, it will push the next sphere (through their connecting spring),
which will push the next one, and so on. Overall this causes an advancing
phenomenon which traverses through the entire string.

  If you *pull* the first sphere, it will pull the next one, which will
pull the next one, and so on. Again, the overall effect advances in the
same direction and the pushing did.

  If you think what a loudspeaker does, it's exact that: By using air
pressure it "pushes" and "pulls" air alternatively. When it does so in
fast succession, our ears perceive these differential waves as sound.

-- 
                                                          - Warp

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