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Lecture plot_wave 


A basic Fourier transform can convert a function in the time domain
to a function in the frequency domain. For example, consider a sound
wave where the amplitude is varying with time. We can use a discrete
Fourier transform on the sound wave and get the frequency spectrum.

This is plot_wave.wav 
plot_wave.wav




This is plot_waved.wav   sin  canged to  cos
plot_waved.wav



This is plot_waved2.wav  derivative of plot_wave
plot_waved2.wav



Java files to produce above:
plot_wave.java
plot_waved.java
plot_waved2.java
plot_wave.mws
plot_wave_mws.out


Above made using:
plot_fft.m reads .dat amplitudes
wav_to_dat.c make .dat from .wav

cat.wav, sound file, was converted cat.dat, amplitude data file
cat.wav sound
cat.dat amplitude in 18,814 time steps


square_wave_gen.c using series
square_wave_gen_c.out cos and sin

A more general program for the FFT of large data in Java is:
Cxfft.java
read_wav.java reads and writes .wav
read_wave_java.out output
these may be combined for use in HW5.
fft_wav.java transform and inverse
fft_frame.java with a very crude frequency plot
 very crude frequency plot

Python using downloaded  numpy  has fft
testfft.py
testfft.out
fftwav.py3
fftwav.py3_out
write_ran_wav.py3
plotwav.py3
print_afile.py3

 
MatLab has fft as well as almost every other function
test_fft.m
test_fft_m.out
test_fft2.m
test_fft2_m.out


Reading and Writing  .wav  files for HW5

Here is a program that just reads a .wav file and writes a copy,
and does a little printing. This with extensions can be the basis
of Homework 5. fftwav.py3 , fft1_wav.c ,  You may modify
to suit your desires. These only work for single channel, 8 bit
per sample PCM .wav files. (not all the .wav files listed below)

Note: sound does not work from a remote computer, e.g. ssh
Some programs require special libraries or operating systems.

read_wav.c
read_wav.out
train1.wav
short_count.wav
rocky4.wav
cat.wav

Splitting out read and write wav:
rw_wav.h
rw_wav.c
test_rw_wav.c
test_rw_wav.out

And here are three .wav files from very small to larger for testing:
ok.wav
train.wav
roll.wav
short_count.wav

Suppose you wanted to compute a sound. Here is a generator for
a simple sine wave. It sounds cruddy.
sine_wav.c
sine_wav.out
sine.wav

P.S. When using MediaPlayer or QuickTime be sure to close the
file before trying to rewrite it.
Your web browser can usually play  .wav  files.
Use  file:///  path to your directory /xxx.wav


In Java, ClipPlayer.java reads and
plays .wav and other files. The driver program is  ClipPlayerTest.java


In Python, M$ only, with the WX graphics available, play .wav files with
sound.py
or on linux 
linux_sound.py
rocky4.wav


In MatLab play  .wav, old wave replaced by audio,
must be on local computer with speaker.  
waveplay.m
short_count.wav

Im MatLab play .dat files that have a value for each
sample.
soundplay.m
short_count.dat

Here is Rocky speaking and the dynamic spectrum 
rocky4.wav
This needs modifications for 2 channel and 16 bits per sample.





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