7/3/2015hillenbrand: source filter theory1 source-filter theory source-filter theory can be used to...

04/19/23 Hillenbrand: Source Filter Theory 1

Source-Filter TheorySource-filter theory can be used to describe and explain any kind of speech – vowels, consonants, periodic, aperiodic, mixed, static, dynamic, you name it.

Our initial goal is to understand the application of SFT to just one simple thing: production of a sustained, phonated vowel. We’ll then see how SFT can be used to described anything and everything related to speech.

The Source of Source-Filter Theory (during phonated speech)

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http://www.youtube.com/watch?v=g9D-kUEp03c

Source-Filter Theory Demonstration: Peter Frampton’s Talk Box

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The source does not have to be the larynx and it does not have to be periodic. For example, the source for unvoiced fricatives is produced in the vocal tract rather than the larynx and is (roughly) white noise. The pictures below show SF models for /s/ and /ʃ/.

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/s/ and /ʃ/ SF Models Overlaid

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Previous examples: Unvarying source, unvarying filter.

Everyday speech: Dynamic; i.e., source changes in pitch (f0), loudness (intensity), and quality (FRC) over time; filter varies over time as the articulators move.

Source-filter theory can accommodate the dynamic nature of speech simply by allowing the pitch, loudness, and detailed shape of the source to vary over time and by allowing the vocal tract FRC (i.e., the VT filter) to vary over time as the articulators move from one position to the next.

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This is what the 1st part of time-varying source for “Where were you…” looks like in the frequency domain.

Frequency>

Time-Varying Source Spectrum

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Time-Varying Source Waveform (i.e., time domain)

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Source Only Source Modified by Time-Varying Filter

Time-Varying Vocal Tract Filter

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Sinewave Speech Demonstration

Sinewave speech examples (from HINT sentence intelligibility test):

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Sinewave Speech Example