Sound waves

[Ron Nossaman]

>Since sound travels as a 'compression wave' through, or in, a medium, 
>and in no other way, and since this sort of wave bears no resemblance 
>at all to the waves of the sea, except when graphically illustrated 
>in a cartesian plane -- i.e. it cannot rationally be visualized as 
>anything similar to a "wave" -- then we need to get a right picture 
>of these oscillations in our various media.
>
>I'll stop there and let someone else contradict or clarify or 
>otherwise add to this step in my understanding, emphasizing that the 
>soundboard at this stage need not be at issue.
>
>JD

I see we're right back where we started when I tried to separate internal
compression waves from ripples in a plane. These are different things.
Let's try another analogy. If you hang a blanket on a clothes line, pinned
along one edge, and smack the center of it sharply with something
relatively light, you will see a ring of deformation, a wave, propagating
from the point of excitation to the edges. This is not an internal
compression wave, nor is it a surface wave that doesn't disturb anything
below the surface. The plane is deformed by the initial excitation
displacement, and the resulting deformation propagates across the plane
from the point of origin. After the initial wave reaches the edges, the
overall organization of the plane tends to fall into larger more general
waves of a similar type, though less specific. This is caused by the
boundary conditions, mostly, but is affected by the stiffness and internal
friction of the medium too, as well as the size and shape of the plane
relative to the propagation speed of the wave(s). A soundboard acts in a
very similar manner, except that the plane is stiffer, making the waves
shallower, and the propagation faster. The reflections from the rim of the
piano will affect the resonance patterns as the "echoes" interact with the
initial waves in a sort of vibrational Moire pattern where some waves will
be reinforced, and some canceled by these reflections. It may be sound if
that's the consensus, but it isn't an internal compression wave. There will
be internal compression waves present, but they aren't the primary driver
of the system.

Is that any better a description?

Ron N