> wrote:
> > Dear Experts,
> >
> > Does anyone know if CoolEdit Pro's spectrogram would add
spurious harmonics?
Hi John,
I still have not seen any spurious harmonics in CoolEdit. In fact, I
can not remember of any other major program having such problems.
However, theoretically it would be possible.
A simple test would be to generate a synthetic sine signal, that
does not have any harmonics. When your spectrogram software does not
show harmonics on that signal, your software would be ok.
Filtering would not be a reliable test for that. The reason is, that
there is no ideal low-pass filter, that would remove the signals
from the stop-band (the frequency range above the cutoff frequency)
completely to 100 percent. The stop-band attenuation of common
filters is limited to something like 60 or 90 dB (or even higher),
depending on the type of filter. So, larger signals may remain in
the filtered file (at much lower amplitudes of course). These
remaining signals (or harmonics) visible on a spectrogram were not
produced by the specrogram algorithm. They are really present in the
sound file.
Regards,
Raimund
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