flutter.c

This program creates an digital audio file on your computer that can
be used to help calibrate a flutter meter.  It cannot be used directly
to measure flutter, but it does simulate a tape recorder that suffers
from a known, well-defined percentage of sinusoidal speed modulation.
The function generated is a sine wave whose instantaneous frequency is

   W  + f sin (W  t)
    0           f

where W  is the carrier frequency,
       0

      f  is the (radian) frequency deviation

      W  is the flutter modulation frequency
       f

      t  is time.


Use of the software is illustrated below.  This is a command line
program.  It asks you to enter various specifications about the audio
file you want to produce.  The output computer file format is
Microsoft WAVE, monaural in 16-bit linear PCM.  Most CD writer software
products can translate and copy this onto a standard audio CD ROM, or
you can play the file out on your computer's sound card.

Steve Moshier
November, 2003


$ ./flutterton                          Run the program
File name ? test.wav                    Type in your desired output file name

Sample rate (44100.000) ?               Hit enter to accept the value in parens
44100.000
Frequency ( 3000.000) ?                 This is the carrier frequency
 3000.000
Amplitude (32767.000) ?                 Peak digital waveform amplitude
32767.000
Duration (sec) (   10.000) ?            Length of generated audio segment
   10.000
Peak flutter percent (    1.000) ?      For RMS, use a value 1.414 times larger
    1.000
Flutter frequency (Hz) (    2.000) ?    FM modulation frequency
    2.000
Opened test.wav
Chunk size = 882036                     Output wave file header information
Format chunk size = 16
Format tag is 1 = WAVE_FORMAT_PCM Microsoft
Number of channels = 1
Sample rate = 44100
Average bytes per second = 88200
BlockAlign = 2
Sample size = 16
Data size = 882000


Files in this archive:

test.wav        Output audio produced by the above parameter settings
flutter.exe     DOS or Windows executable
flutter.c       The main program source code
wav.c           Parser and generator of Microsoft WAVE headers
wav.h           WAVE header data structure
makefile        Unix makefile script
msvc6.zip       Microsoft Visual C++ version 6 build scripts
bcb5.zip	Borland Code Builder version 5 build scripts

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  Get flutter.zip:
The URL of this file is http://www.moshier.net/flutter.html.
Last update: 25 November 2003