linearity of mechanical coupling

This question might better be posed on an acoustics group, but my
guess is that someone here will know the answer.


I have been told by knowledgeable acoustics people that when a sound
wave travels through a solid rather than air, the speed of propagation
varies with the frequency (I believe acoustics folks talk about
"bending" as the mechanicsm for propagation). To me this means that if
I mix 2 frequencies together and couple them into a solid, the phase
relationship between the two frequencies will vary as I move my pickup
point along the surfacfe of the solid.

My question is this; does the statement that the speed of propogation
is frequency-dependant also imply non-linearity, and therefore have I
generated new frequencies when I mix several frequencies together? Do
I get distortion with only a single frequency excitation?

If it is non-linear, assuming that I knew the relationship between the
propagation speed and the frequency (for single frequencies), how
would I characterize such a system mathematically?


Thanks for any tips!


Bob Adams
.

Relevant Pages

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