Colored noise

I made the noise in Figure 2 and 3 from random numbers that I filtered spatially to give a lateral coherence on a scale something like the size of a letter--which is somewhat larger than a line (which makes up the letter) width. The noise looks like paper mottling. The spectral color (spatial coherence) of the noise does not affect the results much, if at all. In other words, independent random numbers of the same amplitude yield results that are about the same. I chose this particular noise color to maximize the chance that noise can be recognized on a poor reproduction. We can see on Figure 2 that the noise amplitude is roughly one-third of the signal amplitude. This data thus has a significant amount of noise, but since the signal is bigger than the noise, we should really call this ``good'' data.

Next we will make the noise bigger than the signal and see that we can still solve the problem. We will need more powerful techniques, however.