Reflecting wave energy in piano strings.

[Delwin D Fandrich]

Michael Jorgensen wrote:

> Hello List:
>      How can the reflecting of wave energy back into the string from a
> bearing point(s) be good?  When waves on the water strike a termination,
> such as a beach or seawall, they reflect back offshore forming second
> opposing wave train which messes everything up for quite a distance
> offshore.  We sailors call that a "confused sea".  Wouldn't waves
> reflected around in a piano string do a simular thing? Can a piano
> bridge which floats with the strings respond favorably to a confused
> wave pattern?   Forgive me for a dumb question, but how can this work?
> -Mike Jorgensen RPT

---------------------------------

Mike,

The piano soundboard doesn't really float. It is typically supported around its full perimeter. (OK, so I, and a few others,
have built pianos with soundboards that are not fully supported and "float" along at least part of their parameter.
Unfortunately, we're still in the minority.)

In any case, the bridge, which is the speaking termination of the string, definitely does not float. Because of the physical
nature of the soundboard and rib structure it is fairly resistant to both the longitudinal mode vibrations and the side to
side vibrations from the strings but is somewhat more compliant to the up and down mode (in a grand -- back and forth in an
upright). In a sense, it acts as a filter, accepting energy that is applied perpendicular to the soundboard surface but
rejecting, or resisting, energy applied parallel to its surface.

-- ddf