Regarding John Spradley's question:

"I ran across a statement that Helmholtz built cardboard pipes for use
in his studies of sound.  As I remember it he was attempting to show
that the pipe material didn't matter much (probably only small pipes).
Can anyone shed any light on this?"

Hermann L. F. Helmholtz, M.D., was indeed a remarkable man.  His best
known accomplishments deal with the production and modification of
sound.  All of this was done prior to the availability of microphones
and oscilloscopes.

In perhaps his most famous work he constructed a series of small
acoustical chambers (Helmholtz Resonators) of various sizes and shapes
to study acoustical resonance.  He indeed used cardboard pipes (not
organ pipes) as one of the chamber variables.  The modern ported
loudspeaker enclosure and the equations predicting it's behavior are
derived almost directly from Helmholtz' experiments.  In fact, early
"bass reflex" enclosures were originally called "Helmholtz resonators".

Helmholtz also extensively experimented with organ pipes.  He built
flue and reed pipes and examined pipes built by Silbermann, Cavaille-
Coll, and Smith.  He provides mechanistic explanations for the
influence of pipe shape and also flue and reed design on the tone
produced.  Among his many conclusions is that flue pipes constructed
of softer material sound duller.  90%Pb-10%Sn pipes sound duller than
90%Sn-10%Pb pipes.  Wooden pipes sound duller than metal pipes.  Balsa
wood pipes sound duller than maple wood pipes.  I can find no reference
in Helmholtz' works regarding cardboard as a construction material for
organ pipes.

This work is summarized in the book:

 "Sensations of Tone"
  Hermann L. F. Helmholtz
  Longmans, Green and Company
  London, June 1875
  Translated by A. J. Ellis from Helmholtz' original German text
  entitled "On the Sensations of Tone As A Physiological Basis for
  the Theory of Music", published a few years earlier.

It's rather dry reading but it is the foundation for modern acoustical
theory.  It is certainly an inspirational work.  If you tinker with
organ pipe design it is well worth your time to read this book.  It
will change your way of thinking.

Bill Finch

 [ 90%Pb-10%Sn indicates that the alloy is composed of 90% lead
 [ (plumbum) and 10% tin (stannum).  The added tin helps to prevent
 [ work-hardening due to vibration, and it also lowers the melting
 [ temperature of the alloy.  Common solder is 50%Pb-50%Sn, and solder
 [ for electrical connections is typically 40%Pb-60%Sn.  -- Robbie