Acoustic Theory of Vowel Production and Resonance

the larynx produces

a complex periodic sound

the vocal tract

filters the sound source

harmonics near formant frequencies

resonate and have high amplitudes

harmonics far from formant frequencies

are attenuated (weakened)

Vocal-fold vibration provides

a periodic sound source for vowels and voiced consonants

Noise at the glottis

can provide an aperiodic sound source for the vowels of speech

Both periodic and aperiodic sound sources

excite the resonances of vocal tract cavities

Filter- pharynx

Formed by a tube of constrictor muscles

Filter- oral cavity

Formed by the space between the teeth, upper and lower jaws (maxilla, mandible), and tongu

Major oral landmarks for speech

Teeth (especially incisors), alveolar ridge, velum (soft palate)

Contraction of levator palatini raises velum

closes the velopharyngeal port, separates nasal and pharyngeal cavities, and is used for oral speech sounds

Relaxation of the levator palatini allows velum to drop

opens the VP port, air flows freely into nasal cavity (as in breathing), velum must be lowered for nasal speech sounds

Intrinsic Muscles

four muscles run within the body of the tongue

Superior longitudinal

Raises tongue tip, as for /l/

Inferior longitudinal

Lowers tongue tip, as for /i/

Ventrical muscle

Runs superior inferior, flattens tongue body

Transverse muscle

Runs from left to right, narrows tongue body

periodic sources

core voicing for vowels and voiced consonants, air from lungs pushes past vocal folds in larynx, causing them to open and close

aperiodic sources

generates unvoiced fricatives and sources, air forced through constriction of narrow opening of vocal tract, creating air turbulence

pharynx landmarks - contracting these narrows pharynx

Superior constrictors (at level of nasopharynx), middle constrictors (at level of oropharynx), and inferior constrictors (at level of laryngopharynx)

oral cavity landmarks

teeth (production of dental sounds such as t and d), alveolar ridge (anterior region of hard palate- production of alveolar sounds), and velum (soft palate- production of velar sounds)

extrinsic muscles

four muscles connect tongue with external structures, connect tongue with external structure

tongue movement- styloglossus

up and back, for u

tongue movement- hyoglossus

down and back, as for ɑ

tongue movement- genioglossus

up and forwards for i

tongue movement- palatoglossus

up

lip change shape

oribucularis oris muscle and risorius muscle

Orbicularis oris muscle

encircles lips, used in bilabial closures and lip rounding

Risorius muscle

draws corners of lips back and up, active in lip spreading

acoustic resonator

tube representation of vocal tract, region of glottis and lips can be modeled as a tube that is open at one end and closed at the other

resonance

the result of altering the sound passing through the supraglottal cavities of the vocal tract

glottis

with adducted vocal folds, is the closed end

lips

separated for vowel production, form the open end

supragottal cavities are shaped by

articulators

resonant frequencies determined partly by

cavity size

formants

resonances of the vocal tracts

nodes

closed end (glottis), air pressure is at maximum, air particle velocity must approach zero

antinodes

open end (lips), air pressure is at a minimum, air particle velocity must be at a maximum

nodes

constricting the vocal tract near a pressure maximum (minimal velocity), raises formant frequency

antinodes

constricting near a region of minimum pressure (maximum velocity), lowers formant frequency

hold source constant while changing filter

maintain constant pitch, vary vowel

hold filter constant while changing source

articulate a single vowel, vary f0

Ə 

Created with relatively uniform vocal tract tube , central mid

i

Large pharynx, small oral cavity, high front vowel

Ɑ 

small pharyngeal cavity, large oral cavity, low back vowel

u

Large pharynx, large oral cavity, overall vocal tract lengthened by lip protrusion, high back rounded vowel

F1 and F2 /i/

F1 low, F2 high

F1 and F2 /Ɑ/

F1 high, F2 relatively low

F1 and F2 /u/

F1 low, F2 low

Relative patterns of formant values __ across speakers

consistant

absolute formants __ across speakers

vary

how do absolute formant values vary

Speakers differ in overall vocal-tract length, parts of the vocal tract may differ in size. pharynx is proportionally smaller in women than men, speakers of the same language vary in dialect and idiolect 

low vowels F1

small pharyngeal cavities, large mouth opening, high F1

high vowels F1

large pharyngeal cavities small mouth opening, low F1

Front vowels F2

Small front cavities, high F2

Back vowels F2

Large front cavities, low F2

Rounded vowels F2

lengthen front cavity, low F2. Speakers can trade off lip rounding and tongue backing to produce a low frequency F2

Ranges Men

• F1 250- 750 Hz 

• F2 850-2400 Hz 

• F3 2250-3000 Hz

Ranges Women

• F1 300-900 Hz 

• F2 900-3000 Hz 

• F3 2650-3400 Hz

Congenitally deaf speakers

Often have deviant vowel spaces, jaw and tongue placements are often more constrained than in hearing speakers, the range of formant values is not as great in hearing speakers

Impaired vowel production evident in

apraxia of speech, dysarthria, and cerebral palsy

Foreign accents may involve

errors in vowel production

visual feedback

may help speakers involve vowel productions

attack phase

transition into the vowel

steady state

vowel formants are steady

decay phase

transition into following phoneme

vowels have ____ durations than consonants

longer

vowels have ______ amplitude than consonants

greaters