Sound waves

[Delwin D Fandrich]

----- Original Message -----
From: "Ron Nossaman" <RNossaman@KSCABLE.com>
To: <pianotech@ptg.org>
Sent: December 05, 2001 8:48 PM
Subject: Re: Sound waves


> My problem with the use of the word "sound" here was the impression that
> the soundboard works with internal compression waves. While sound that we
> hear by atmospheric transmission is a pressure wave propagation, the
> pressure wave propagation isn't the primary driver of soundboards. It's
the
> ripples on the surface of the "pond" that produces the bulk of the
pressure
> wave in the air that we hear.
> It's not the word that is the issue, it's the wave form.
>
> Ron N

I've used the ripple in the pond illustration frequently as well, but it
really isn't an accurate one, though if the pond is small enough it can be
quite illustrative.

Once, many long years ago, I tried gluing the rim of a paper plate to a
piece of scrap wood. Then I glued a short piece of wood dowel (a piece of
hammershank) to the approximate center of the paper plate. If you move the
dowel up and down you can see the plate move something like the movement of
the soundboard. Apparently, the plate follows the dowel instantaneously but,
of course, it doesn't. There is some finite time lag between the moment you
move the dowel and the rest of the plate following that movement. That's the
wave moving outward from the dowel to the parameter of the plate. If you
could move the dowel fast enough you would start a new wave moving out while
one or more of the earlier waves was still coming back you could make the
surface of the plate resonate at some frequency.

I think I'll round up some paper plates and see if I can make a soundboard
out of them.

Del