# Lecture 30 Blog, ECE438 Fall 2010, Prof. Boutin

Wednesday November 3, 2010 (Week 11) - See Course Outline.

We began with a couple of exercises to understand the different ways of constructing periodic signals we have seen. We then continued modeling the vocal tract as a sequence of tubes and analyzing this model. We observed that the relationship between the airflow at each end of a cylindrical tube is just a time delay (positive for the air flowing right, and negative for the air flowing left). We wrote this relationship in matrix form. Next lecture, we will describe what happens when the air flows from one cylinder to the next.

Hw9 is now posted. It is due next week. I hope you will have fun analyzing the speech signal of Neil Armstrong as he stepped foot on the moon.

Note: There was a very interesting question on the disccusion page of HW8, which made me realize that I forgot to say the following in class: "Although the FFT makes the computation of a DFT faster on a computer, it does not make it faster for the DFT that we ask you to compute by hand. The idea is that, for N large, the number of operations needed to compute an FFT is much lower than that for computing a DFT using the formula. However, when we ask you to compute a DFT by hand, N is typically very small, so using the FFT usually only makes things more complicated."

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