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

APPENDIX B. PROGRAM LISTINGS 249
/*
Minima.c
By Andrew Botros, 2001-2004.
Modified by Paul Dickens, 2006-2007.
Listing B.14: Minima.c
Characterises the minima of acoustic impedance spectra.
Refer to Minima.h for interface details.
IMPORTANT: Calculations are optimised for a spectrum resolution of
2Hz.
NOTE: The weighting of the frequency of an impedance extremum fit to
favour the absolute emtremum has been changed to an option in the
function 'parabolaExt' with a default of 0 (no weighting). A block
has also been added to the function 'extrema' to handle the case
when the next point to be considered is equal to the previous one
(this fixed a bug in the code).
*/
/* necessary define for some gcc math.h functions */
#ifndef _ISOC99_SOURCE
#define _ISOC99_SOURCE
#endif
#include
#include
#include
#include
#include "Vector.h"
#include "Point.h"
#include "Note.h"
#include "Minima.h"
/* number of data points approximated around each minimum */
#define NUM_POINTS 11
/* number of points which must be consecutively increasing or
decreasing to define the spectrum as rising or dropping. */
#define TWEAK 5
/* weight fit to absolute extremum? */
#define WEIGHT 0
/* to evaluate harmonics, a window is defined around the frequency f
of the fundamental minimum: f +/- HARMONIC_WINDOW/100. Minima which
lie within integer multiples of this window are deemed to be
harmonics. */
#define HARMONIC_WINDOW 5.0
/* maximum number of harmonics used to calculate average impedance of
harmonics */
#define HARMONICS_AVERAGED 3
Vector minima(Vector allpoints) {
int i, j;
Vector extv = extrema(allpoints);
Extremum e, searche;