SPPA 403 Speech Science 1

Unit 3 outline

• The Vocal Tract (VT)• Source-Filter Theory

of Speech Production• Capturing Speech

Dynamics• The Vowels• The Diphthongs• The Glides• The Liquids

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Articulation: Lecture Outline

• Brief anatomy review

• Introduction to Source-Filter Theory

• Introduction to tube acoustics

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Supraglottal (Articulatory) system

• Comprised of– Cavities– Articulators

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Supraglottal Cavities?

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• Oral

• Nasal

• Pharyngeal

• (Buccal)-cavity between the teeth and cheek

Supraglottal Cavities

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nasal cavity

oral cavity

pharyngealcavity

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The vocal tract

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Immobile articulators?

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Immobile articulators

• Hard palate

• Teeth

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Hard Palate

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Teeth

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Mobile articulators?

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Mobile articulators

• Pharyngeal walls

• Soft Palate

• Mandible

• Tongue

• Face, lips and cheeks

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Pharyngeal walls

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Soft palate

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Mandible

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Tongue

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Face, lips and cheeks

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The vocal tract

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Unit 3 outline

• The Vocal Tract (VT)• Source-Filter Theory of Speech

Production• Capturing Speech Dynamics• The Vowels• The Diphthongs• The Glides• The Liquids

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Simplifying the vocal tract into “tubes” and “valves”

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Simplifying the vocal tract into “tubes” and “valves”

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The “tube” and “valve” analogy

• Tubes…– Act as an acoustic resonator or filter

• Valves…– Open and close the vocal tract to some tubes

• velopharyngeal port• Oral articulator approximations

– Serve as sound source• Larynx (glottal spectrum)• Within the vocal tract (i.e. /s/)

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Source-filter theory of speech production

• The sounds we hear as speech is a function of– Sound source– Vocal tract filtering

• source and the filter are independent of each other

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Source-filter theory simplified

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Name that vowel!

Same source, different filters

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“Larynx? We don’t need no stinking larynx…”

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Source characteristics

• The source – does not have to be the larynx– does not have to be periodic

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Passing white noise through the filter

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Passing white noise through the filter

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Same source, different filters

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Vocal tract as a tube

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Vocal tract as a tube

• Tubes have physical characteristics

• Tubes are acoustic resonators

• Acoustic resonators have frequency response curves (FRC)

• Physical characteristics dictate FRC

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Note

• Frequency response curve is also termed the transfer function

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Frequency response curve (FRC)

• FRC peaks – resonant or formant frequency

• Resonators have an infinite number of formants

• F1, F2, F3 … denotes formants from low to high frequency

F1 F2 F3 F4

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Vocal tract as a tube (Figure 9-1)

Vocal tract: bent tube, closed at one end, with differing Cross-sectional diameter.

Straight tube, closed at one end,of differing cross-sectionaldiameter

Straight tube, closed at one end,with a uniform cross-sectionaldiameter

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Characteristics affecting filter properties

• Length.

• Cross-sectional area along its length.

• Whether it is closed at either or both ends.

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Area function of a tube

…

Are

a (c

m2)

Length along tube (cm)

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Area function of a tube

• Area function dictates the frequency response curve for that tube

Are

a (c

m2)

Length along tube (cm)

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Uniform tube (unchanging area function) closed at one end

• First resonance or formant

F1 = c/4l

Where

c=speed of sound (35,000 cm/sec)

l = length of the tube

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Uniform tube closed at one end

• Higher resonant frequencies or formants are odd multiples of F1

For example,

• F1 = (c/4l )*1

• F2 = (c/4l )*3

• F3 = (c/4l )*5

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Tube example

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What about the vocal tract?

• The vocal tract is fairly uniform in its cross-sectional diameter for neutral or central vowel (schwa)

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Male vocal tract

Average length 17.5 cm

F1 = (35000/4(17.5))*1 = 1*35000/70 = 500 Hz

F2 = (35000/4(17.5))*3 = 1500 Hz

F3 = (35000/4(17.5))*5= 2500 Hz

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Female vocal tract

Average length 14 cm

F1 = (34000/4(14))*1 = 1*35000/56 = 607 Hz

F2 = (35000/4(14))*3 = 1821 Hz

F3 = (35000/4(14))*5= 3035 Hz

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Male-female comparison

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Articulation in the context of source-filter theory

• neutral vocal tract configuration is an example of an articulatory configuration

• Articulation systematically changes– the filter properties of the vocal tract– the type of sound source