Klarinet Archive - Posting 000081.txt from 2002/06

From: w7wright@-----.net (William Wright)
Subj: [kl] Benade vs. Materials..... again
Date: Tue, 4 Jun 2002 12:19:46 -0400

It has been stated here on Klarinet many times that "the experiment has
been done, and materials do not make a difference." But I have never
seen a citation for a specific experiment or explanation of the methods
used.

Benade *does* discuss a few cases, and he gives specific observations.
His remarks cause me to wonder, once again, whether the statement that
"the experiment has been done" is really true.

Here are a few quotations from "Fundamentals of Musical Acoustics",
Chapter 22, section 7, titled "The Effect of Wall Material on the
Playing Properties of Wind Instruments".

Benade's examples make me think, once again, that the lead tape
experiment --- which I have discussed several times previously --- may
truly tell us something, one way or the other.

==================================

When identical woodwind air columns are made using wall materials of
different porosity or rigidity, the resulting sounding pitch of the
instrument may vary by as much as twenty cents; thin-walled instruments
on which one can feel vibrations

[NOTE: the phrase "feel vibrations", and similar statements below,
raises the distinction between a wall that vibrates and an instrument
that 'rebounds' or 'recoils' in its entirety. When experiments were
done, was the instrument clamped in a massive vise and hence only wall
vibration was being measured? I wish I remembered enough physics to
calculate an instrument's inertia in comparison to the total energy
input of a person's breath. This wouldn't say anything about how the
energy is used once it enters the air column, but it would be an
interesting number.]

are often improved (but sometimes spoiled) by putting layers of adhesive
tape on the outer surface at an empirically chosen spot [....] For
instance, it has been known that the walls of a perfectly round pipe
cannot vibrate enough to radiate audible sounds into the room.

[NOTE: clearly he is talking about radiation from walls that vibrate
here, not about recoil of the entire instrument. I have omitted
several paragraphs about round vs. elliptical pipes, but Benade's
concluding statement is:]

Because of this, changes in the material or the thickness of the walls
cannot detectably alter the sound of an instrument insofar as it depends
on radiation by the walls.

[NOTE: I omitted several pages that discuss turbulence caused by rough
walls, sharp edges, and so forth --- all of which are the result of the
different machinability of various materials. These are differences in
air column geometry, and everyone agrees that they make a difference,
and therefore I'm not considering them here.]

================================

A concluding comment; We cannot "feel" directly what our diaphragms
are doing. Nor can we identify precisely (or even 'almost precisely')
what our tongues are doing inside our mouths.

Just because we declare that we cannot consciously identify a particular
frequency or volume, it does not does not follow that our overall sense
of 'sound character' is unaffected. (We should think of the
synesthesia discussion that we had last week. Patients are often
unaware of their shortcomings in perception, yet the results are
dramatic!)

Benade's discussion includes several qualifications similar to the one
that I have quoted above. I repeat a similar qualification from a
different paragraph:

"[....] but even so it cannot radiate sound into the room with
sufficient amplitude to be heard in the presence of other sources of
excitation. Because of this, changes in the material or the thickness
of the walls cannot DETECTABLY [emphasis mine] alter the sound of an
instrument insofar as it depends on radiation by the walls."

Cheers,
Bill

================

If I had Stadler's mouthpiece, would I play better? Or do I need his
ligature also? Or perhaps he and I are different persons? If I had
Mozart's pen, would I compose better?

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