Sound waves(The behavior of soundboards)

[Greg Newell]

John and interested parties,
    I have been following this only sporadically but this post has brought a
simple question to mind. John, you have determined that there are 2 distinctly
different sounds derived from striking the top or the side of a bridge. Can this
be duplicated outside the piano? Is this done in some way while the piano is
still strung? Can this be repeated with a piece of maple (or other bridge
material ... ?????) outside the piano perhaps with bridge pins or nails driven
in only one side? If this is ridiculous I'll go away quietly.

Greg

John Delacour wrote:

> At 5:05 PM -0600 12/18/01, Ron Nossaman wrote:
> >  >Problem 2:
> >  >
> >>a)  I take a small tack hammer and tap the bridge lightly but firmly
> >>on its top.  I then give a similar tap with the hammer on the side of
> >>the bridge.  The difference in the sound produced is very markedly
> >>different in the two cases.  It needs no trained ear to tell them
> >>apart.
> >>
> >>b)  I take a tuning fork or small tone generator and apply it first
> >>to the top of the bridge and then to the side of the bridge.  The
> >>sound emitted from the soundboard is the same in both cases.
> >
> >Let me see if I have this straight. You want me to diagnose what happens in
> >the bridge before the soundboard moves enough to make the noise by which
> >I'm to judge what happens in the bridge before the soundboard moves? Isn't
> >that basically the problem with this discussion? This isn't even
> >conceptually possible, much less arguable.
>
> Fiddle-de-dee! I stated the problem very clearly.  I am asking you to
> "diagnose" nothing but simply to explain to me and the list why
> hammering the bridge from the two directions results in two very
> different qualities and quantities of noise, whereas applying a
> tuning fork respectively to the side of the bridge and to the top of
> the bridge results in two sounds that are virtually identical.  All
> that is needed to answer the question is a basic understanding of
> what is happening, an understanding that this whole discussion has
> given you ample opportunity to gain but which you have stedfastly
> refused to absorb.
>
> >  What you need is
> >instrumentation. A few accelerometers on the bridge on various planes, next
> >to a string, and a few on the soundboard. All of them wired to the
> >appropriate millisecond timing device. Hit the string with a hammer and
> >look at the accelerometer data to see which moves first - the bridge or the
> >soundboard. If the soundboard moves first, you win. I'm backing the bridge.
>
> Humbug!  I don't give a fart about winning.  That's your line of business.
>
> >  >Problem 3:
> >>
> >>Why can't I use the tack hammer to drive in tuning pins.  Why does it
> >>just bounce off the punch and fly up to the ceiling?
> >>
> >>Answer me those.
> >>
> >>JD
> >
> >And this has what to do with bridges and soundboards?
>
> If you can't see the connexion after having three people attempt at
> great length to get you to see, then I must assume there is no point
> in further clarification.

--
Greg Newell
mailto:gnewell@ameritech.net