Klarinet Archive - Posting 000173.txt from 2001/12

From: "Keith" <100012.1302@-----.com>
Subj: [kl] Materials
Date: Sat, 8 Dec 2001 11:13:04 -0500

Re: Materials:

>>Walter Grabner says: Here's my problem when we bring up science. None of
us are SCIENTISTS!

Well, I'm a seriously reputable scientist in my field, which is materials
science, with specialities in X-ray scattering theory and the analysis and
metrology of materials. I'm an amateur clarinettist and amateur woodworker.
It does not make me an authority in what is happening in musical acoustics,
and certainly does not help me to answer Walter's other question: "Who on
this list can tell me scientifically why one tone is better than another, or
why note for note Robert Marcellus played better than "XYZ"?", though I can
see that there might indeed eventually be scientific answers to these
questions. But it does allow me to understand and to weigh the evidence
available.

Everyone interested in this topic should read Arthur Benade's classic
"Fundamentals of Musical Acoustics" in which he discusses the evidence on
this topic, from his own and others' careful measurements over a few
decades. To summarise (hopefully without oversimplification), this shows:

1. The energy radiated into the room (heard by the listener) by the
vibrating walls of a wind instrument is far, far outweighed by the energy
radiated by the tone holes, at all frequencies. Unless the instrument is
very thin-walled this cannot be a source of differences in perceived tone.
You need to go to string instruments to get big influences of the material.
(As an aside, there is a cello made by the local blacksmith out of iron
plate in the museum in Devizes, UK, but I don;t know how it sounds!)

2. On the other hand the energy radiated by the tone holes is far outweighed
by the energy needed to counteract the damping caused by vibration of the
instrument walls, porosity in the material, skin friction (affected by
surface roughness) and oscillatory temperature effects. Most of the player's
energy input goes into feeding the vibrations of the instrument. But the
wall damping does not vary significantly between woods, and various metals
if the walls are reasonably thick, and if they are smooth and non-porous.
Benade takes 2% variation as the threshold "that most musicians are able to
detect" in this regard. Porosity will certainly make a difference, and so
will a rough bore (leading to the conclusion that oiling does make a
difference!). So there may be a minor influence of material here. Balsa wood
would definitely feel very different (and hard work) because of the
porosity.

3. The vibrations of the air column can most definitely be influenced by
material. The air column "looks oversize" at points of large wall vibration
if the natural frequency of the wall lies above that of the air mode that
drives it and undersize when this relationship is reversed. Thin-walled
instruments can have their behaviour changed radically by putting adhesive
tape on certain spots. Pad material has a significant influence. All of
these contribute to the mix of partials that give us the tone of a note.
This does not tell us whether a particular material is "better".

4. There are secondary effects of materials, already referred to by others,
which come from the different manufacturing techniques and tools used. Cut
or polished wooden, metal or delrin surfaces can easily be distinguished
topographically. Some materials (eg injection-moulded plastics) lend
themselves to the production of sharp internal tone hole corners, which are
extremely bad news for playability since they give rise to local turbulence
in the tone holes. (After reading Benade's book many years ago, I attacked
the cheap plastic bass clarinet on which I had a fearsome solo to play
[Britten's Albert Herring], took off all the sharp tone hole edges with
emery paper and fear and trembling, and to my great relief made an
unplayable instrument quite passable.

So, could you make instruments out of different materials that sound and
play identically? In principle, almost certainly. Do we, {as a class of
scientists, instrument makers and players) know well enough what we are
doing to achieve this? Certainly not. It is pretty complex and less
advanced, compared with my own field. The experience and skill of craftsmen
working in material they know, understand and love plus the long tradition
in wooden instruments, in my view, much outweighs what science and
technology can currently offer. But all experiments, such as those Walter
reported, should be encouraged as this is the way instruments will improve.

And what am I doing myself? Most of my instruments are grenadilla; I have a
metal contrabass; and after much discussion with Stephen Fox on workability
and effects of the low Denver humidity on various woods, I have ordered a
cocobolo/gold basset horn like Dan's, because it looks drop-dead gorgeous,
Stephen likes making them, and my heirs will thank me. I am less optimistic
than Dan that it will create a nubile fan club for me.

Keith Bowen

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