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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Supraglottal Cavities
•
•
•
•
Oral
Nasal
Pharyngeal
(Buccal)-cavity between the teeth and cheek
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nasal cavity
oral cavity
pharyngeal
cavity
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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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Same source, different filters
Name that vowel!
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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)
F1 F2
F3
F4
• FRC peaks –
resonant or formant
frequency
• Resonators have an
infinite number of
formants
• F1, F2, F3 … denotes
formants from low to
high frequency
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Vocal tract as a tube (Figure 91)
Straight tube, closed at one end,
with a uniform cross-sectional
diameter
Straight tube, closed at one end,
of differing cross-sectional
diameter
Vocal tract: bent tube, closed
at one end, with differing
Cross-sectional diameter.
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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
Area (cm2)
…
Length along
tube (cm)
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Area function of a tube
Area (cm2)
• Area function dictates the frequency
response curve for that tube
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 crosssectional 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
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