In [20]: 
from __future__ import division
import numpy as np
import matplotlib.pyplot as pt
In [21]: 
wave = 60*load("cs450.npy")
In [22]: 
plot(wave)
Out[22]:
[<matplotlib.lines.Line2D at 0x69a00d0>]
In [23]: 
from simple_audio import play
play(wave)
In [5]: 
n = 256

integers = arange(n)

omega = exp(1j*2*np.pi/n)
dft_matrix = omega ** (integers * integers[:, newaxis])

inv_dft_matrix = 1./n*dft_matrix.T.conj()
In [6]: 
chunked = wave.reshape(-1, n)
transformed = np.dot(inv_dft_matrix, chunked.T).T
In [8]: 
imshow(log10(1e-4+abs(transformed)).T); colorbar()
Out[8]:
<matplotlib.colorbar.Colorbar instance at 0x4f95320>
In [17]: 
modified = transformed.copy()

#modified[:,5:-5] *= 1e-2

#modified *= 1e-2
#modified[:,5:-5] /= 1e-2

nshift = 3
modified.fill(0)
modified[:, nshift:n/2] = transformed[:, 0:n/2-nshift]
modified[:, n/2:n-nshift] = transformed[:, n/2+nshift:]

imshow(log10(1e-4+abs(modified)).T); colorbar()

-c:10: DeprecationWarning: using a non-integer number instead of an integer will result in an error in the future
-c:11: DeprecationWarning: using a non-integer number instead of an integer will result in an error in the future
Out[17]:
<matplotlib.colorbar.Colorbar instance at 0x6477c68>
In [18]: 
chunked = modified.reshape(-1, n)
result = np.dot(dft_matrix, chunked.T).T

result = result.reshape(-1)
In [19]: 
play(result.real)
In [13]: 
play(wave.real)
In []: