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

102 CHAPTER 6. MATERIAL AND SURFACE EFFECTS
10 9 Frequency (Hz)
10 8
pre−treatment
after 5 weeks of treatment
1 week post−treatment
|Z| (Pa s m −3 )
10 7
10 6
10 5
10 4
0 500 1000 1500 2000 2500 3000 3500 4000
Figure 6.6: Impedance spectra for pipe 5 before, during and one week after treatment.
was not available at UNSW during the course of candidature.
6.4 FURTHER INVESTIGATIONS
In this study there seem to be three different contributors to the effect of surface conditions on
acoustic impedance spectra. These are the macroscopic roughness (increased by humidity),
how wet the surface is (increased by humidity) and whether the wood is oiled. These contributors
are entangled in this study, and an attempt should be made to look at them in isolation.
In future work it may be useful to repeat this experiment with wood more suited for flute
making. Any changes in acoustic impedance spectra would likely be of much smaller magnitude
than found in this study, but would be more relevant to players and makers of wooden
flutes. Such work may well answer questions about the best way to oil and play in a new instrument,
especially if combined with surface microscopy (perhaps using ESEM).
Flute players and makers speak of gradual improvement in flute bores over time as they
are repeatedly oiled and polished by the cleaning swab. In this experiment, none of the pipes
showed less attenuation after treatment (with the possible exception of pipe 4). This is likely
because of the huge macroscopic surface changes in a softwood like radiata pine when exposed
to humid air. It may be possible to chart such changes in a hardwood such as is used in flute
making.