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

CHAPTER 8. SOFTWARE IMPLEMENTATION 114
and the output line for a single note contains the information
[numHarm] [meanHarmZ]
Typical output is
60 3.0 3.9 261.8 1 98.4 12 104.0
61 3.0 3.9 276.8 -2 98.3 12 104.3
62 3.0 3.8 293.4 -2 98.2 11 104.5
...
A playability value of 3.0 indicates that the note is easily playable, while 1.0 is difficult to
play. Likewise, a note with a strength of 4.0 is strong and bright while 1.0 is weak and dark.
8.1.6 ‘Waves’
The process ‘Waves’ calculates and outputs the relative magnitudes of pressure and flow along
the bore of an instrument. The usage is as follows:
Usage: Waves [OPTIONS]
Options:
-s
-r (default 2.0)
:
- Optional if no holes are defined in XML file.
- Must be a sequence of 'O' (open hole) and 'X' (closed hole)
characters.
- Length must be equal to the number of defined holes.
- e.g. "XXOOOOOOXOOOOXOOO"
The required argument midi is the MIDI number for the played note and frequency is the
frequency of interest (usually a resonant frequency, as obtained from ‘AnalyseNotes’). ‘Waves’ is
implemented in the C program file Waves.c (Listing B.29) and relies on functions in Woodwind.
h and Woodwind.c.
‘Waves’ calculates the pressure p in and volume flow U in at the input to the played instrument
in relative units such that |p in | 2 + |Z 0 U in | 2 = 1 Pa 2 , where Z 0 is the characteristic impedance
at the input to the instrument. The pressure p(x) and volume flow U (x) are calculated at
points along the instrument bore xres mm apart. The output of the program is a list of tabdelimited
x, |p(x)| and Z 0 |U (x)| triplets, such as
-16.0 0.111 0.002
-14.0 0.111 0.004
-12.0 0.111 0.006
-10.0 0.111 0.009
-8.0 0.112 0.011
-6.0 0.112 0.013
-4.0 0.112 0.016
-2.0 0.112 0.018
0.0 0.110 1.619