Unit 4 Articulation I.The Stops II.The Fricatives III.The Affricates IV.The Nasals.

Unit 4Articulation

I. The Stops

II. The Fricatives

III. The Affricates

IV. The Nasals

Stops

• Place– Bilabial /p/ /b/– Alveolar /t/ /d/– Velar /k/ /g/

• Voicing– Voiced /b/ /d/ /g/– Voiceless /p/ /t/ /k/

Stops: Articulatory manner

Sequence

1. Complete VT occlusion

2. Oral pressure positive– ~equal to subglottal P– 5-10 cm water

3. Rapid VT opening

4. Oral pressure=ambient

If VoicelessVocal folds abduct

Vocal folds adduct

Stops

• Occlusion and release results in two important feature of stops

• Acoustic silence, observed during build up of oral pressure

• Transient, aperiodic sound generated during the release of pressure

Stops: VCV time domain

Stops: VCV time domain

vowel vowel

burst

silent gap/closure interval

voice onset time

Stops: characteristic features

• Silent gap/closure interval

• Release burst

• Voice onset time

• Formant transitions

silent gap/closure interval

• Period during VT occlusion

• Often absent or reduced in voiced stops

• Voiced stops have voicing into and often throughout the closure interval

• How can voicing continue with a closed vocal tract?

Silent gap/closure interval

voiceless

voiced voice bar

Stops: characteristic features

• Silent gap/closure interval

• Release burst

• Voice onset time

• Formant transitions

Release burst

• transient (doesn’t last long)

• aperiodic (a wide range of frequencies, no harmonic structure)

• lasts 10-30 msec

• Often absent when stop is in the final position

Release burst

Release burst

• Informative about place of articulation• Related to the size of cavity in front of

constriction• Bilabial: diffuse energy dominant in low

frequency (500-1500 Hz)• Alveolar: diffuse energy that is dominant in

higher frequencies (2500-4000 Hz)• Velar: compact energy in midrange (1500-4000

Hz)

Release burst

bilabial

alveolar

velar

Aspiration

• Observed in voiceless stops

• Consequence of air turbulence at the open glottis

• Increases the duration of the release burst

Stops: characteristic features

• Silent gap/closure interval

• Release burst

• Voice onset time (VOT)

• Formant transitions

Voice onset time

• Time between release and onset of phonation

• Considered to reflect laryngeal/articulatory coordination

• Is longer for voiceless than voiced stops

Voice onset time

voiceless

voiced

Voice onset time

• For voiced stops, VOT can be• Short lag: vocal folds vibrate shortly after

release• Simultaneous voicing: VOT = 0 since

voicing and release are coincident• Prevoicing VOT lead: VOT <0 since

voicing occurs before release• VOT ranges from –20 – 20 msec

Voice onset time

• For voiceless stops, VOT is

• Termed long lag

• VOT ranges from 25 – 100 msec

Voice onset time

• Place of articulation is distinguished by VOT

• Bilabial: relatively short VOT

• Alveolar: mid-length VOT

• Velar: relatively long VOT

• RULE: as the cavity in front of the occlusion gets longer, VOT increases

Stops: characteristic features

• Silent gap/closure interval

• Release burst

• Voice onset time

• Formant transitions

Formant Transitions

• Formants of adjacent vowels will change with VT occlusion

• Transitions will last about 50 msec (shorter than glides/liquids)

• Transitions not obvious with voiceless• The form of the transition is a function of

– The place of articulation– The neighboring sound– F1 and F2 are the key players

Formant Transitions

• Place of articulation

• Bilabial– F1 starting value: close to 0 Hz– F2 starting value: ~ 600-800 Hz– F1 & F2 will usually rise toward the formants

of the adjacent sound

Formant transitions: bilabial

ahb

Formant Transitions

• Place of articulation

• Alveolar– F1 starting value: close to 0 Hz– F2 starting value: ~ 1800 Hz– F1 will always rise and F2 will go up or down

depending on the preceding and following vowels

Formant transitions: alveolar

ahd

Formant Transitions

• Place of articulation• Velar

– F1 starting value: close to 0 Hz– F2 starting value: ~ 1300 Hz when followed by a back vowel~ 2300 Hz when followed by a front vowel– F1 will always rise and F2 will go down– F3 is helpful with velars, typically the F2-F3 transition

is ‘wedge-shaped’ F2 going up, F3 going down

Formant transitions: velar

ahg

Formant transition: voiced vs. voiceless

voiceless

voiced

An important point…

• When discussing source-filter theory, the sound source was the glottal spectrum

• When discussing stops (and fricatives and affricates), we introduce a new sound source, noise produced within the oral cavity

• However, source-filter theory still holds even though the sound source is different…the vocal tract still filters the sound source, whether it is the complex periodic signal from vocal fold vibration, or a transient aperiodic signal produced during a stop release