2.3 Audio Signals – Instruments

Here a repertory of audio signals of different instruments is at your command. You can visualize and view their frequency spectra by using the FFT. After working with filters and following IFFT calculation the appropriate audio signals can be generated.
The FFT and IFFT calculations are carried out by NumPy, a free software for computating numerical problems, on a server. This calculation might take a few minutes.

After choosing an instrument its audio signal is graphed.
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 the 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.


By clicking on the button "IFFT calculation" the appropriate audio signal is generated out of the filtered frequency spectrum and can be viewed.
The graph is a function of time.