>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
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