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Formant Filters, Part I

March 9, 2012
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I’ve been pretty interested in making filters in Reaktor lately, and today I came across a few that seemed interesting and potentially useful. These are taken from the paper Software for a cascade/parallel formant synthesizer by Dennis Klatt, but I first came across them here.

Translating these structures into Reaktor is a trivial task. The triangles symbolize gain (IE, multiply) modules, the + is obviously an adder, and the z-1 is the symbol for a unit delay, and is already available as a module in Core. So we won’t need to design anything complicated, simply plug in the Reaktor equivalents to the flow chart’s structure:

Filter A) Resonator

Filter B) Antiresonator


As you can see, the Reaktor structures are a piece by piece reconstruction of the flow chart. Most digital filter designs have a similar structure, in fact these are each basically one half of the biquad filters I posted earlier, the difference being how the coefficients are generated. The math to calculate the coefficients is given in Klatt’s text and can easily be duplicated in Reaktor. Note that the Antiresonator has a frequency response that is the mirror image of the Resonator’s frequency response (it cuts the bands that the resonator boosts and vice versa).

These filters are often cascaded to create vowel-like formants, which is exactly what I intend to do with them. Hopefully I’ll have more on that project soon, until then, you can grab the filters here.

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2 Comments leave one →
  1. March 12, 2012 10:40 am

    It’s so fascinating to see these principles in action, and experiment using tools like Reaktor. Makes me wish I’d paid more attention in math class. Great work, keep it up!!

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  1. Formant Filters, Part II « salamanderangram

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