My inquiry is regarding the so called cepstrum analysis.
By conducting some experiments, i have real time data at my disposal. The acquisition rate is 1600Hz.
I wanted to try cepstrum analysis just out of curiosity to see how it performs in comparison with trivial spectral analysis.
So what i do with the acquired data:
- Use a lowpass filter with a cut-off frequency of 340 Hz for noise attenutation.
- Fourier transform the filtered data, removing the DC component by subtracting the mean value from the filtered data.
- Take the log of the magnitude of the FFT.
- Apply IFFT on the resulting vector to acquire the real cepstrum.
I notice that, despite the filtering that has taken place at step 1, the cepstrum plot displays activity beyond the cut-off frequencies. So my question is this: Is this supposed to happen? To me it seems that this is not normal. Does anyone have any experience with that?
Edit: Plot image added for clarification. Frequencies of interest lie on the right of the red line displayed