the features stored in vector

[Xiao Z]

In textbooks, it writes the vector stores some information feature like fricative or something like that.
But in your slide, a vector representing square wave stores the parameters of sine wave components. And according to FA, every waveform can be represented by simple sine waves, thus I deduce spectral information is the same.

So what exactly are stored in the vector of an observation? Are those acoustic features also some values representing simple sine wave components?

[Simon]

At this point in the course, it is indeed a little mysterious what is in the feature vectors. There’s a good reason for keeping you all in suspense: we need to know more about the generative model before making a final decision about the feature vectors.

In other words, we cannot do our feature engineering correctly until we know exactly what properties the generative model has. Specifically, we will need to know its limitations (what it can not model).

So, for now, let us pretend that the feature vector contains one of these possible sets of features:

• the FFT co-efficients, or
• the formant frequencies, or
• the energy in different frequency bands (a “filterbank”)

The mystery will be solved within a few lectures, when we will learn about MFCCs.

[Author]

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