What allows oral constiction gestures to be systematically distinguished from one another?
- shared across members of the community (parity)
- not confusable with one another under a variety of speaking conditions.
(1) Anatomically distinct constrictors
- tongue tip
- tongue dorsum
Shared by all members of the community
Decomposition of body into distinct organs is at least partially innate.
These contrast in all languages.
Distinct constrictions emerge in early babbling of infants.
MacNeilage and Davis theory: Infants only oscillate their jaws, and depending on the posture of their tongues, they produce what adults hear as or [de] or [gu].
(2) Constriction degree
how partitioned into discrete regions that are systematically distinguished across speakers?
Quantal Theory of Speech (Stevens, 1968, 1989)
Examine relation between:
dimensions of physical device and sound produced
Experiment with a straw
Results of experiment: map relating opening and sound
There are stable and transition regions in the map.
Small change in opening do not effect sound
Small change in opening shifts from one stable region to another.
Stevens' Quantal Theory
Stable and transition regions generally characterize relations between dimensions of sound producing devices and the sounds they produce.
This is true of the human vocal tract.
The nonlinear nature of this map partitions a potential gestural continuum into distinct stable regions.
Languages employ contrastive gestures that are produced in distinct stable regions of the map relating articulation and sound. why?
Example: Constriction Degree
Interaction of Constriction Degree and Voicing
- Produce [v]
- Widen constriction until turbulence disappears.
- Now stop voicing
- Turbulence is back, why?
Turbulent flow of a liquid (or gas) involves generation of random (or chaotic) patterns of molecular vibration.
It depends on:
- Channel size
Narrower channels more readily cause turbulence.
- Volume velocity (cm3/sec) of airflow
Higher airflow rates more readily cause turbulence.
Reynolds Number (Re) is a dimensionless quantity that takes both into account.
A given channel area (CD, constriction degree) will have different Reynold's number (Re), depending on the volume velocity of the flow.
Turbulent flow will result at a particular Re threshold (for speech conditions, Re=1700), and the intensity of the generated turbulence will increase as Reynolds number increases above threshold.
In general, voicing reduces volume velocity (glottis is closed roughly half the time).
Re> 1700 for voiceless flow rates
Re< 1700 for voiced flow rates
Effects of voicing and turbulence interaction on gestural patterning in languages
statistical rarity of voiced fricatives
Aerodynamic conditions for voiced fricatives
Voicing: subglottal pressure > oral pressure
Turbulence: oral pressure > outside pressure
What happens to them?
to preserve turbulence, voicing may be lost
- loss of turbulence
to preserve voicing, constriction degree may increase
CD can be partitioned into four regions (Catford, 1977):
turbulent if voiceless
Lateral vs. central fricatives
- constriction degree
- articulator tension
Constrictors that can trill:
Constriction Degree of trills
intermediate between stop and fricative
articulators touch, but are not compressed: CD = ~0
Summary of constriction degrees (from Catford, 1977):