Extending SF Theory to
Accommodate Articulatory Movement
Static Vowels ►
Diphthongs ► Semivowels ► Stops
[ɑ]
[i]
[u]
This shows the formant patterns for 3 static
vowels. English has 3 diphthongs (nonstatic) that
include these vowel qualities: [ai] (buy), [au] (bow),
and [oi] (boy). (You may have learned different ways to
transcribe these sounds; don’t worry about it.)
What patterns would you expect for [ai], [au], and
[oi]?
natural
[ai]
[au]
[oi]
synthetic
The principle is straightforward: to get [ai], you
start around [A] and transition into something
around [i]. Same idea with [au] and [oi]. These
dynamic changes in formants are called formant
transitions. They’re a very big deal – for vowels
and for consonants.
natural
[ai]
[au]
[ɔi]
synthetic
The synthetic copies here are purposely
cartoonish – I connected the formants for the
1st vowel to those of the 2nd vowel with straight
lines. The ear doesn’t seem to be real fussy
about the fine details.
Ok, let’s review what we’re trying to do here
– how do we extend the simple (and very
limiting) static SF model we’ve been working
with to a dynamic SF model that we need to
understand how actual speech works.
At this point we’ve extended a static vowel
model to a dynamic vowel model. It may not
seem like we’ve gone that far, but we have –
all the rest of the steps will look very similar.
Next steps:
1. Push the dynamic vowel idea to the most
vowel-like consonants: semivowels
(glides).
2. Push the semivowel idea to the least
vowel-like consonants: stops.
[uA]
[wA]
[bA]
[iA]
[jA]
[gA]
[uA]
[iA]
[wA]
[jA]
[bA]
[gA]
Going left to right, the sound category (manner
class) is changing – diphthong ► semivowel ► stop.
What is the articulatory feature that distinguishes
these three manner class categories?
What is the acoustic feature that distinguishes
these three manner class categories?
[uɑ]
[iɑ]
[wɑ]
[jɑ]
[bɑ]
[gɑ]
Articulatory difference: speed of articulatory
movement – diphthongs: slow movements;
semivowels: medium speed; stops: very fast.
Acoustic difference: formant transition duration –
diphthongs: long transitions; semivowels: mediumlength transitions; stops: very short transitons.
[uA]
[iA]
[wA]
[jA]
[bA]
[gA]
One quick point before we move to the next
question: These articulatory and acoustic facts
have to be connected in this way. Articulation
controls sound: if the articulators move slowly, the
formants have no choice but to change slowly; if
the articulators move quickly, the formants have no
choice but to move quickly.
[uA]
[iA]
[wA]
[jA]
[bA]
[gA]
Comparing top to bottom ([uA] vs [iA], [wA] vs. [jA], etc.), the
sounds differ in the starting articulatory configuration.
Top row is simple: They’re all labial sounds.
Bottom row not quite so simple, but they all start with a
high tongue position, then move to [A].
For simplicity, we’re going to call the top-bottom difference
place of articulation.
[uA]
[iA]
[wA]
[jA]
[bA]
[gA]
Ok, we’re going to characterize differences between
[u]-[i], [w]-[j], and [b]-[w] as place of articulation.
The terminology is a slight stretch, but conceptually
it works fine. Top row: labials, bottom row: we’ll call
these “palatals” for convenience.
Now the question: What acoustic information
conveys these “place” differences to the listener?
[uA]
[iA]
[wA]
[jA]
[bA]
[gA]
Two possibilities can be ruled out: (1) F1 rises for
both “places”; that can’t be it. (2) F3 slants
downward for the “palatals”; that could be it, but it’s
not. Just trust me.
What’s left?
Bottom line:
This particular manner class difference
(diphthongs vs. semivowels vs. stops)
is conveyed by differences in formant
transition duration (due to differences
in the speed of articulatory movement).
Differences in place of articulation are
conveyed by differences in the
trajectory of F2 (and sometimes F3)
transitions.