Lecture 6: Articulatory Physiology

Question 1

What is coarticulation?

Answer 1

• When “two articulators are moving at the same time for different phonemes” (Borden, et al., 1994)
• Only happens when the gesture that overlaps will not cause a change in the identification of other sounds
• Say “two” – lips are rounding for [u] when saying “t”

Question 2

What are the articulatory, acoustic, and aerodynamic events in stops and fricatives?

Answer 2

STOPS

Articulatory event: Closure interval

• Acoustic: period of quiet
• Aerodynamic: increase in oral pressure (Po)
• Greater Po for voiceless than voiced

Articulatory Event: Release of constriction

• Acoustic: burst – noise generated due to turbulent airflow through articulators as they begin to open
• Aerodynamic: fast decrease in Po and increase in oral airflow (Vo)
• Vo greater for voiceless than voiced

Articulatory Event: just prior to onset of vocal fold vibration for vowel following consonant

• Acoustic: aspiration – noise generated by turbulent airflow moving through the vocal folds as they are nearly approximated for the onset of vocal fold vibration for the vowel

FRICATIVES

Articulatory event: close approximation of the articulators

• Acoustic: frication – Noise generated by turbulent airflow moving through the small space between the two articulators

Articulatory event: close approximation of the articulators

• Aerodynamic: High Po, but not as high as for stops. However, Po maintained over a longer period of time
  
  • Higher for voiceless than voiced
• High Vo
  
  • Higher for voiceless than voiced
  • Double peaked airflow waveform – 1st peak is airflow as the articulators come close together, 2nd peak is airflow as the articulators move apart at the end of the fricative

Question 3

How does pharyngeal expansion occur and why it is necessary to continue voicing during a stop?

Answer 3

• During complete occlusion of the vocal tract:
• Build up of Po behind the occlusion
• Po will eventually equal Ps unless something is done to keep this from happening
• Need to maintain the pressure differential between the subglottal space and the supraglottal space for vocal fold vibration to continue
• Use pharyngeal expansion to keep Po < Ps
• This increases the size of the pharyngeal cavity
• Leads to a decrease in Po
• Keeps Po from increasing enough to equal Ps
• Active mechanism: cranio-caudal expansion:
• Elevate velum using levator veli palatini
• Lower larynx using sternohyoid
• Passive mechanism: transverse expansion:
• Relax pharyngeal constrictor muscles
• Superior, middle, and inferior constrictors
• Makes walls of pharynx compliant, so increase in Po pushes walls out passively