[sdiy] 1-2-4 !

[Yves.Usson at imag.fr]

Well, I quickly ran a simulation with a carrier at 20Hz and a modulation at
2Hz.
The generated signals for one second are summarized in the attached GIF file.
>From a spectral point of view :
in the first case (one quadrant)we have a mixture with a high DC component,
a strong 2Hz component (modulation, M), a small 18Hz component, 
a strong 20Hz component (carrier, C) and small 22Hz component. 
It is in fact the mixture of the DC, the modulation frequency, 
the carrier frequency and two frequencies that are respectively,
the difference of frequencies (C-M) and the sum of frequencies (C+M).
In the second case (two quadrants) we have a small 18Hz
component a strong 20Hz component and small 22Hz component.
In the third case (four quadrants) we have a strong 18Hz
component and a strong 22Hz component (the carrier and modulation
signals are nulled).

>From a sound "point of view", the four quadrants case is certainly the more
dramatic and interesting, ideal to create nice bell sounds. With one quadrant
and two quadrants you can achieve dramatic dialeks' voices. 
Exterrrminaaaaate !

Cheers


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