compression waves

[Richard Brekne]

Might I point out to you two that the fact that the frequencies of the LM are
effected by the speaking length in no way necessarilly bears on whether or not
those frequencies can run along the whole of the string unneffected by
boundries ?

This is also born out by the rod experiment that I posted a link to the other
day. The frequencies of the LM is determined by where the clamp on the rod is
placed, but that in no way affects either the presence or the strength of those
frequencies on the other side of that clamp.

I am also building a monochord to see if I can show exactly this behavior.

RicB

Ron Nossaman wrote:

> >>What i did say is that I believe  [!!] bridges are transparent to
> longitudinal
> >>modes.........highly unlikely that any external clamping mechanism
> >>will be able to prevent the internal wave transmission past it, as
> >>long as the molecular structure is continuous. Transmission waves
> >>simply pass right past these clamped bits. They will eventually be
> >>reflected when they reach the geometric and physical _end_ of the
> >>bar, or localized discontinuities.
> >
> >This contradicts Conklin's finding (which I have verified) that the
> >frequency of the wave is a function of the speaking length.  As I
> >mentioned yesterday, the propping up of the speaking length with a
> >_simple_ bridge, by which I mean the equivalent of a low violin
> >bridge, is of course adequate to change the base frequency of the
> >transverse waves but will not affect that of the compression wave.
> >By contrast, anything in the nature of a firm clamp, which includes
> >the clamping effect of a piano bridge, does serve as a termination
> >(broadly speaking) of the wire with respect also to the main
> >compression wave.  I say nothing of its harmonics, since I haven't
> >tested these.
>
> This is very similar to the results I just got with a quick and dirty
> monochord. A round, unanchored "bridge" didn't much affect LM1, but a
> solidly anchored pinned bridge, like one found in an actual "modern" piano,
> produces an LM1 dependant on the speaking length. A piano like bridge
> doesn't, by my observation, seem to be transparent to LM.
>
> Ron N




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