[PD] Spectrum graphing amplitude problem
Martin Peach
martin.peach at sympatico.ca
Mon Oct 22 21:06:36 CEST 2007
Mathieu Bouchard wrote:
>A very simple way to explain aliased frequencies would be: spin a bicycle
>wheel. When you accelerate it beyond a certain point, it will begin to look
>like it's going backwards instead. This is because the wheel speed,
>together with the repetitiveness of the wheel's appearance, have crossed
>the Nyquist frequency of your eye.
That won't work in sunlight for example. You need a flashing light source
like a fluorescent tube. It's the Nyquist frequency of the light source that
causes the aliasing, not of your eyes, unless you try it while blinking
rapidly. The wagon wheels in western movies appear to turn backwards when
the spokes are moving faster than the frame rate of the movie.
Martin
More information about the Pd-list
mailing list