[PD] Spectrum graphing amplitude problem

[Martin Peach]

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