Reflecting wave energy in piano strings.

[Robert Scott]

At 01:06 PM 11/17/97 +0000, 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.

  If all of the energy from the travelling wave in the string
went into the bearing point on the bridge and none of it was reflected,
then there would only be one cycle of sound - no sustain.  As it
is, only a small portion of the energy is transferred to the
bearing point.  Most of it is reflected.  This forms a standing
wave in the string, complete with nodes for each partial.  I
suppose "messed up" is one way to describe the confusion that goes
on in a piano string.  It is not a simple picture.  Perhaps it
is a little simpler than the water analogy though, side water
waves are two-dimensional and the waves is a string are
one-dimensional (if you don't consider precession).

Bob Scott
Ann Arbor, Michigan