Here you see a speech signal, which is overlaid with the sound of a vuvuzela.
After the frequency spectrum is represented by using the FFT the frequency of
the vuvuzela can be filtered. After having used the IFFT the filtered speech
signal shall be better hearable.
The FFT and the IFFT calculations are carried out by NumPy, a free software
for computating numerical problems, on a server. This calculation might take
a few minutes.
This image shows a speech signal, which is overlaid with the sound
of a vuvuzela. The spoken sentence is hardly understandable. In order
to understand the speaker better the noise of the vuvuzela needs to
be filtered as well as possible.
The graph is a function of time.
After clicking on the button "FFT calculation" the frequency spectrum
of the audio signal is shown.
So a function of frequency has been produced out of a function of time. Now you can see
the signal′s frequencies with the absolute values of the Fourier transformed.
By moving the appropriate controllers (red) the frequencies, that shall be filtered,
(horizontal controllers: bass and treble filter) as well as the intensity of filtration
(vertical controller) can be varied. So the task is to identify the vuvuzela frequencies
in order to filter them.
By clicking on the button "IFFT calculation" the appropriate signal is
generated out of the filtered frequency spectrum and can be viewed.
Now you can hear, whether the right frequencies have been filtered or whether you
need to go back to the previous application and change the controller settings.
The graph is a function of time again.