Articulation and Resonance Articulation: Movement of structures along the vocal tract that change...

Articulation and Resonance

Articulation: Movement of structures along the vocal tract that change the resonance properties of the cavities in the V. tract These movements change the physical properties

(surface area, volume) of the different cavities Changing the surface area/volume of different cavities

produces different amounts or air at different locations The air mass will help determine the frequency at which the

air in the vocal tract vibrates


Cavities of the vocal tract: Pharynx Consider the structure, shape, and the ways in which

the pharyngeal shape and surface area can be changed Wall of muscle forming posterior wall of vocal tract Shape varied through the contraction of 3 main groups

of muscles Inferior @ level of larynx Middle @ level of hyoid Superior @ level of palate/mandible

The musculature changes the size of different portions of the pharynx, allowing energy at different freqs. to resonate


Cavities of the vocal tract: Pharynx The pharyngeal cavity is often compared to a bottle

filled with air – blowing across the top of the bottle sets the air in the bottle into motion

The air source in the pharynx, however, may be periodic as well as aperiodic During phonation, the source is periodic, which will affect the

pitch of the vocal tract output Pharyngeal constrictors affect the amount of air in the

pharynx by changing the cross sectional area at different locations


Generation of different sounds Periodic - when phonated

Produces a harmonic complex in which harmonic frequencies are integer multiples of the F0

Aperiodic – for example whispering or frication in which the vocal folds slightly abducted so that they don’t vibrate, but allow a turbulent flow of air through

Flow of air blocked completely by some articulator (stop consonants, plosives)

Flow of air partially blocked and passed for a greater duration than when stopped (sibilants)

Combined sound sources Refers primarily to voicing being produced concurrently with

some form of constriction (stops, fricatives that are voiced)


Vowel production: Periodic sounds Typically modeled by considering the vocal tract a

series of coupled resonators Vowel spectrum can be predicted from size and shape

of the cavities

For vowels - Vocal tract considered a tube closed at one end Powered by harmonic energy The size of the average male vocal tract, for example,

produces resonances at 500, 1500, and 2500 Hz when it is not constricted at any location (schwa)


Vocal tract resonances: Formants Affected by physical characteristics discussed thus far

that include cross-sectional area of cavities, vocal tract length, and F0

Named with regard to their frequency relative to other vocal tract resonances For example, F1 is always lower in frequency than F2, which

is always lower in frequency than F3, etc.

The source-filter theory provides predictions of formant frequencies based upon the nature and location of vocal tract constrictions


Source-Filter theory The subglottal air pressure is the power source for

speech The vocal tract filters the power, or flow of air, by

producing resonances related to the shape of the cavities through which the air flows

The talker has control over the shape of the cavities, therefore, the filtering action is intentional, and designed to produce sufficient contrast between speech sounds Because resonances depend on the specific locations of

constrictions, there is no longer a simple mathematical relationship between formant frequencies the way there is between harmonics and a fundamental


Source-Filter theory The sub-glottal power source stimulates the air of the

vocal tract at F0 and at harmonic frequencies Harmonics are frequency components of complex sounds that

are present at integer multiples of F0 Therefore 2nd Haromonic=2 x F0 3rd Harmonic=3 x F0, etc.

Harmonic frequencies and formant frequency are often different The harmonics fill the sound spectrum, their overall level is

shaped by the VT resonaces In this way, energy filling a part of the spectrum at which a

resonance occurs, it will be passed more efficiently than at other frequencies

Formants and Harmonics


Depictions of vocal output Spectrograms – wide band and narrow band Assess frequency, intensity, the amount of time

Distinguish harmonics from formants The intensity of formants is obviously higher Can also observe change in formant frequency as vowel

identity is changed as in the production of a dipthong The visible differences between formants is consistent

with the articulatory, and auditory distinction

http://library.thinkquest.org/19537/

http://library.thinkquest.org/19537/


Vowel Production: The “point” vowels /i/ - high, front, unrounded vowel - indicates the

location of the tongue, which forms the constriction; and whether the lips are rounded or not characterised by a high F2 & F3, and a low F1

Size of oral cavity dictates F2 Front vs. back constriction drives F3, in which front

increases F3, back constriction lowers it Therefore /i/ has a low F1, and a high F2 and F3


Vowel Production: The “point” vowels /i/ - for the vowel /i/ the constrictions are placed

according to what we know will be perceived as /i/ The constriction size can be measured using x-rays that take

cross sectional slices of the vocal tract (OH) For this vowel, the constriction is near the lips, at the

end of the oral cavity, and the lower vocal tract is opened wide Tongue is raised and fronted using the genioglossus muscle Forms a small cavity in top “bottle” and a large cavity in the

pharynx



Vowel Production: The “point” vowels Again, formants are not necessarily centered at

harmonic frequencies But they reinforce certain frequency regions, and

energy in these regions will be more intense at the opening of the mouth

We should then expect these formants to fall at different frequencies across different vowels

Some examples:


Vowel Production: The “point” vowels /a/ low, back vowel

Must increase size of oral cavity by actively lowering jaw and/or lowering tongue

Jaw lowering with anterior belly of digastric Tongue lowering with hyoglossus

Lowered jaw and tongue constrict oropharynx, producing larger oral cavity, smaller pharyngeal cavity Note diff. formant freqs and their association to cavity sizes Discernable using tactile sense (talker), & acoustic and visual

senses (listener) High F1, Low F2


/i/ /a/


Vowel Production: The “point” vowels /u/ high, back vowel Constriction at back of mouth, rather than front Tongue raised by styloglossus (raises and backs toward

styloid process) Lips are protruded, lengthening v. tract, which lowers

all formants Posterior constriction pulls tongue back, enlarging oral

cavity Produces a low F1 and low F2.

/a//i/


/u/

x

x

x


Relation between tongue position and output spectra Further forward tongue is placed

Higher F2 Further back

Lower F2, and a tendency to raise F1 Up

Lowers F1, and raises F2 Down

Raises F1, and lowers F2 However, position of the tongue is not as important as

where the narrowest constriction is made (may be made in the pharynx regardless of the tongue’s position)

/i/ /u/

/u//i/

/Ɛ/ /I/

/I//Ɛ/


Consonant production Resonant consonants

Semivowels, the glides /w/, /j/, and liquids /r/, /l/ have formant structures similar to vowels, but appear, in syllables, in the places that consonants appear (car, not crt)

The nasal consonants Use of the velopharyngeal port modifies v. tract /m/, /n/, /ng/

“REAL”


Consonant production The nasal consonants

The velopharyngeal port is closed by backing the velum to the posterior pharyngeal wall - although different degrees of closure will be accomplished by raising the velum to different heights

Velopharyngeal port also responsible for adjusting the volume, and therefore the pressure, in the cavities above the larynx

Incorrect function can produce hypernasality, which is produced by too much air leaking into nasal cavity

Or hyponasality, which is produced by too little air passing through the nasal cavity


Consonant production Nonresonant consonants - fricatives

Restricted flow of air, when compared to semivowels and nasals, therefore, no formant structure to speak of

Constriction causes turbulence and an aperiodic flow of air The noise produced will resonate (just like blowing across the

top of a bottle) effectively in the cavity immediately anterior to the turbulence

This is usually the front of the mouth, or the space between the lips and teeth


/life/ /aspire/


“MEAN”


Consonant production Fricatives

labiodental (/f/, /v/) for which voicing produces the important distinction

linguadental (/th/, /the/) – again, voicing is the difference Alveolar (/s/, /z/) Palatal (/sh/, /zh/)

The stops - sounds produced when the V. tract is most thoroughly occluded (ptk, bdg) moving from constriction in the front of the mouth to

constriction at the rear changes the identity of the consonant from labial /p,b/ to velar /k,g/

/th aw/ /s aw/ /sh aw/ /ch aw/


“CHURCH”


“SAVE”


Consonant-Vowel combinations (CVs) Rely upon rapid movements of articulators

Constrictions required for consonants Open, or dilated cavities required for vowels The rapid movements of articulators produce rapid changes in

formant frequency, called formant transitions These are considered important acoustic cues for speech

perception The further the articulators move, the greater the change in

frequency resulting from the articulatory manipulation


/bab/, /dad/, /gag/


Voice-onset time Amount of time needed for voiced air to reach the exit

of the oral cavity is VOT Longer as the constriction is moved further back

Voiceless stops have longer VOT than unvoiced for /b/, voicing begins as the lips remain closed, and so upon

release, the air flow is associated with voicing for /p/ there is a preceding burst of air before the folds are

adducted (peter vs. beater)

/b/

/p/

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Articulation and Resonance Articulation: Movement of structures along the vocal tract that change...

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