note_filter_test.py

## Found code from: http://stackoverflow.com/questions/18625085/how-to-plot-a-wav-file
import matplotlib.pyplot as plt
import numpy as np
import wave
import sys

def filterNote(noteFreq, omega, transform):
	filterRange = 10
	minFreq = noteFreq - filterRange
	maxFreq = noteFreq + filterRange
	filteredSignal = []
	for index, frequency in enumerate(omega):
		if (frequency > minFreq and frequency < maxFreq):
			filteredSignal.append(transform[index])
		else:
			filteredSignal.append(0)
	return filteredSignal

#Open the wave file
spf = wave.open('52_piano_notes.wav','r')

#Extract Raw Audio from Wav File
#Becuase this particular file is too big. 
#For smaller files, use -1
print "reading frames"
signal = spf.readframes(-1)

#Make the frames into an array of integers
print "converting to integer array"
signal = np.fromstring(signal, 'Int16')

#Get the frame rate of the file
print "getting frame rate"
fs = spf.getframerate()

#Get an array of time values. We know the frame rate
#And the number of frames, so the array is easy
Time=np.linspace(0, len(signal)/fs, num=len(signal))

#Plot the wave
plt.figure(1)
plt.title('Signal Wave...')
plt.plot(Time,signal)
#plt.xlim([3.1,3.105])

#Transforms yay!
print "transforming"
transform = np.fft.fft(signal)
omega=np.linspace(-20000, 20000, num=len(transform))
plt.figure(2)
plt.title('Fourier Transform of Signal')
plt.plot(omega, transform)

print "filtering"
noteTransform = filterNote(440,omega,transform)

plt.figure(3)
plt.title('Filtered Note')
plt.plot(omega,noteTransform)

plt.show()