Lecture #13 - Using the DFT

Question 1

What are two important issues that come up when using theDFT

Answer 1

1. Choice of window
2. Use of zero-padding

Question 2

Let’s say we have two sounds and plot its FT

What happens when the frequencies of these sounds gets closer

Answer 2

. The amplitude of the two signals interfere with each other. This interaction is called leakage.

The component at one frequency leaks into the vicinity of the another component.

Question 3

What is effective spectral resolution of the DFT determined by?

Answer 3

Determined by the spectrum of the windowing function and NOT the number of points N

Question 4

How does zero-padding work?

Answer 4

1. Before taking the DFT, add zeroes at the end of the sequence to increase length
2. Does not change information in the signal
3. Increase the length of the DFT and hence the number of points on the DFT spectrum

Question 5

Does zero-padding improve the resolution of spectral components?

Answer 5

No, it simply interpolates