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# Long description

This is four repeats of the frequency-domain representation from Figure 33. In each case, part of the graph is shaded to show what would be removed by the filter.

In part (a), a small vertical section is shaded around the 1.221 kilokertz line.

In part (b), everything at a higher frequency than just above the 1.221 kilohertz line is shaded.

In part (c), everything at a lower frequency than just below the 1.221 kilohertz line is shaded.

In part (d), everything is shaded except for a small vertical section around the 1.221 kilokertz line.