Flute acoustics: measurement, modelling and design - School of ...

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Chapter VI
Material and surface effects
6.1 INTRODUCTION
The material of which a flute is made is thought by some to affect the sound quality of the resulting
instrument, but several studies (Coltman 1971, Widholm et al. 2001) have shown that
players and hearers of the flute cannot distinguish between flutes made from a variety of different
materials. Coltman compared keyless flutes made from silver, copper and grenadilla wood
each played with the same headjoint made from Delrin plastic. Widholm et al. compared entire
flutes of identical design made from solid silver, 9 carat gold, 14 carat gold, 24 carat gold and
solid platinum, as well as platinum plated and silver plated flutes. For the study of Coltman, ‘no
statistically significant correlation between the listeners’ scores and the material of the instrument
body was found’ while Widholm et al. conclude that there is ‘no evidence that the wall
material has any appreciable effect on the sound color or dynamic range of the instrument’.
The materials used in both of these studies were all good containers of air—i.e. they were
non-porous or of very low porosity and they were able to be machined accurately and hold a
good edge. In the study of Coltman the headjoint was the same for each flute body, so variations
in the edge-holding ability of each material were not important. When entire flutes are made
from wood, the situation is somewhat different. Different timbers will respond to machining in
different ways and will have different surface characteristics and porosities. Different timbers
are also likely to respond differently to playing and may change to a greater or lesser extent with
time. The acoustic properties of timber flutes are reputed to change over time, particularly
in the first few weeks of playing (see ).
These changes are most likely due to changes in the surface structure of the timber.
6.2 MATERIALS AND METHODS
In an attempt to evaluate the changes in a timber flute over the first few weeks of use, the
impedance spectra of five wooden pipes were measured repeatedly over several weeks while
the pipes were exposed to warm humid air.
The pipes were made from radiata pine, a plantation softwood timber. This timber is far too
coarse, soft and porous for flute making. However it was used in this study to gain a qualitative
appreciation of the effect of temperature, humidity and oiling on the impedance of timber
flutes. The results are therefore an upper bound on the effects that should be expected for typical
flute timbers. Each pipe was turned on a lathe to an outside diameter of approx. 20 mm and
then drilled and reamed to a conical bore profile. The entry and exit diameters of the pipes were
approx. 15 and 12 mm respectively and the pipes were approx. 120 mm in length. As part of this
study, Terry McGee made a keyless classical flute from the same timber. The flute was played