Play with the DFT

1.

Pick up the Maple worksheet named hw9_demo.mws from the web page and run through it, comparing the implementation of the DFT with the description in the book. You will have to work with and modify this implementation, so read it carefully.

2.

Make sure that you can answer the following questions:

(a)

What is the sampling rate? The critical frequency?

(b)

What is the meaning of the f_n? How do you interpret the horizontal axis in the figure? See page 406.

(c)

Why are the amiplitudes at the positive frequencies the same as the amplitudes at the negative frequencies?

3.

You might want to change the way the DFT is plotted so that it only shows the positive frequencies, or so the horizontal axis is labelled correctly.