Sound waves(The behavior of soundboards)

[Richard Brekne]

John Delacour wrote:

> At 9:33 AM +0100 1/21/02, Richard Brekne wrote:
> >I found this article that has a several basic definitions and some
> >good illustrations.  Amoung them right at the start of the article a
> >good illustration of a transverse wave in solids. This illustration
> >along with some descriptions I have recieved recently from a few
> >kind souls satisfy one of the problems I was having with this
> >transverse wave explanation.
> >
> >http://www.geology.uiuc.edu/~hsui/classes/geo351/LectureNotes/waves.pdf
>
> I downloaded this paper and found no mention of bending waves.  I was
> already doubtful before I downloaded it, having seen geology in the
> URI.  In seismic phenomena there are types of wave that do not
> concern us.

I don't believe I said anything about bending waves per se in that reference
John. That term was not connected directly with the reason I posted the
article. I posted it exactly for the reason I stated and for no other
reasons. So I am not surpassed you find it doesn't meet some other
criteria.  It has, regardless of its foundation in geology, some basic terms
and concepts relative to waves and sound propagation in general, and so I
posted it.

>
> I have sent you off-list an illustration of a Bending Wave and
> emphasized that the use of the expression "transverse bending wave"
> is a contradiction in terms.  The term Flexural Wave is used
> interchangably with Bending Wave, but it is quite distinct from a
> Transverse Wave, as I will explain below.

I have looked and looked for such a interchangeable usage of these terms,
and come up with only one source that uses the terms "Flexural" and
"Bending", in any context that resembles what you describe. That would be
Dr. Russell's site again and his definition of this wave type is that of a
dispersive (speed is frequency dependent) "quasi longitudinal" wave.  Note
that does not say directly that these are compression waves. As compression
waves otherwise seem to be non dispersive in nature I have to wonder if this
is more a matter of descriptive use of terms then it is anything else. But
what do I know ?  I can tell you that the 4th order differential equation
Russell gives for the speed of such a wave is identical to that given in
Fletcher and Rossing in their description of Bending waves, (page 58)  which
they define as transverse.

Of course all this would be very flattering to myself having first mentioned
quasi compression waves in this koneksjon, but I suppose I would rather hang
on to Dr. Askenfelts rather direct answer to my question on the matter in
lea of some other evidence or authority on the subject.

Otherwise I can confirm that the terms "Bending" and "Flexural" seem
interchangeable enough, but just about everywhere I look they refer to a
transverse wave when they are, and I have yet to find them concretely
defined as a purely compressive wave.  Could you provide some suggested
reading that directly makes these assertions then ?

>
>
> snipp---
>
> JD




--
Richard Brekne
RPT, N.P.T.F.
Bergen, Norway
mailto:rbrekne@broadpark.no
http://home.broadpark.no/~rbrekne/ricmain.html