Sinusoid with Noise, Frequency domain filtering.
Besides using the difference equation 'filtering' can also be
done in the frequency domain using the DFT or more realistically the FFT. The applets illustrate 2 possible simple approaches.
For the first case shown below, the spectrum of the signal calculated.
The resulting spectrum is used to generate an 'output' by deleting
the low amplitude components in the spectrum and finding the inverse transform of what remains. The input is shown in magenta and the
output in yellow.
The level below which spectral components are rejected can be changed by
The applet below illustrate a different approach where all frequencies
in a certain range are deleted. The bandwidth which is rejected can be changed by
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COPYRIGHT © 2007 Cuthbert Nyack.