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[MUSIC PLAYING - "JESU, JOY OF MAN'S DESIRING" BY JOHANN SEBASTIAN BACH] PROFESSOR: Well, up 'til now, I suppose, we've been learning about a lot of techniques for organizing big programs, symbolic manipulation a bit, some of the technology that you use for establishing languages, one in terms of another, which is used for organizing very large programs. In fact, the nicest programs I know look more like a pile of languages than like a decomposition of a problem into parts. Well, I suppose at this point, there are still, however, a few mysteries about how this sort of stuff works. And so what we'd like to do now is diverge from the plan of telling you how to organize big programs, and rather tell you something about the mechanisms by which these things can be made to work. The main reason for this is demystification, if you will, that we have a lot of mysteries left, like exactly how it is the case that a program is controlled, how a computer kno...

[MUSIC PLAYING - "JESU, JOY OF MAN'S DESIRING" BY JOHANN SEBASTIAN BACH] PROFESSOR: Well, up 'til now, I suppose, we've been learning about a lot of techniques for organizing big programs, symbolic manipulation a bit, some of the technology that you use for establishing languages, one in terms of another, which is used for organizing very large programs. In fact, the nicest programs I know look more like a pile of languages than like a decomposition of a problem into parts. Well, I suppose at this point, there are still, however, a few mysteries about how this sort of stuff works. And so what we'd like to do now is diverge from the plan of telling you how to organize big programs, and rather tell you something about the mechanisms by which these things can be made to work. The main reason for this is demystification, if you will, that we have a lot of mysteries left, like exactly how it is the case that a program is controlled, how a computer kno...

[AUDIO PLAYBACK] - Good morning, class. [END PLAYBACK] MICHALE FEE: Hey, let's go ahead and get started. So we're going to finish spectral analysis today. So we are going to learn how to make a graphical representation like this of the spectral and temporal structure of time series, or in this case, a speech signal recorded on a microphone. Well, actually let me just tell you exactly what it is that we're looking at here. So this is a spectrogram that displays the amount of power in this signal as a function of time and as a function of frequency. So you remember we've been learning how to construct the spectrum of a signal. And today, we're going to learn how to construct a representation like this, called a spectrogram, that shows how that spectrum varies over time. So as you recall, we have learned how to compute the Fourier transform of a signal. This is one of the signals that we actually started with. So if you compute the Fourier transform of th...