Sound waves(The behavior of soundboards)

[Richard Brekne]

Stephen Birkett wrote:

> Richard wrote:
> > As I have said... it seems to me that the wave IS the motion. Transverse waves can
> > only exist when two differing medium are involved. Can you picture a "wire of
> > water" in a "lake of water" vibrating transversely ? Of course not. You have three
> > basic medium types. Liquids, solids, and gas. The mechanics of vibration are
> > described by wave mechanics, and that, difficult as it may be to accept, gets into
> > all this about molecular displacement.
>
> Transverse waves can exist only in solids. Liquids and gases will not support shear
> stress which is the technical basis for transverse waves. Surface waves in water are
> not transverse waves and they are fundamentally different from the transverse waves of
> 1-D wires and 2-D membranes.

Ah ! Stephen... was wondering when you would pop in.  I think I have said several times
that the surface waves in this pond example appear to be more part of the compression
waves under the surface then they are actaully transverse in the the sense of  1-D wires
and 2-D membranes.  That Transverse waves can only exist in solids makes perfect sense
when you first point that out. Tho that doesnt conflict really with saying two different
mediums have to be involved or  what ?... hmmm I suppose an absolute vacume is not a
medium... still.

But you say something here that also has made me scratch my head several times and I am
still not satisfied with my view of it so far, and that is this about the difference
between transverse waves and surface waves. Surface waves seem to behave very transverse
like in some respects, certainly visually. Tho I cant manage to see how they can really
seperated from compression waves under the surface, they obviously are somewhat different
in that they seem to opererate as a kind of go between for two different medium types. Is
there a name for these ? Do they occur in all mediums. I suppose they must occur when any
differing mediums meet, but does that include say two solids of different densities ?



--
Richard Brekne
RPT, N.P.T.F.
Bergen, Norway
mailto:rbrekne@broadpark.no