Pulse trains

[Sandy F]

How is a pulse train helpful input for an LP equation? Is it basically a simulation of vocal fold closures? Is the pulse train the same no matter what kind of speech you’re trying to produce?

[Simon]

Yes, a pulse train is an approximation to the sound produced by vocal fold vibration.

Although it might not seem like a particularly good approximation, it is simple and mathematically convenient. The principal difference between a pulse train and the true signal, is that the pulse train has a flat spectral envelope.

That’s not a problem though: we can include the modelling of the actual spectral envelope of the vocal fold signal in the vocal tract filter.

In other respects, the pulse train has the correct properties: specifically, it has energy at every multiple of F0 (a “comb-like” or “line” spectrum).

So, we can say that a source-filter model is really a model of the signal, and not a literal model of the physics of speech production.

[Author]

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