1. Stop + Approximant Acoustics
November 28, 2012

2. Updates Formant measuring exercise has been graded…
Fricative + stop transcription exercise is still due on Friday.
Production Exercise #4 due on Monday after the weekend…
By the way: Production Exam!

3. Voiced Aspirated
Some languages distinguish between (breathy) voiced aspirated and voiceless aspirated stops and affricates.
Check out Hindi:

4. [phal]

5. voiced + breathy aspirated
Hindi
[dhol]
voiced + aspirated
Bengali

6. Zhu|hoasi Stop Contrasts
Zhu|hoasi is spoken in northern Namibia.

7. Last but not least, Korean makes an interesting distinction between “emphatic” (or fortis) obstruents and unaspirated (lenis) and aspirated obstruents.

8. What’s going on here?
A variety of things are going on in the articulation of fortis consonants in Korean.
Glottis does not open as wide as in lenis stops.
Voicing begins more quickly after stop release
Vocal folds are more tense than in lenis stops.
Increased airflow in fortis stops.
Higher F0 after stop release.

9. A Basic Distinction Vowels
Relatively unconstricted flow of air through vocal tract (above the glottis)
Shape (filter) the source of sound made at the glottis
Consonants
Completely or severely constricted flow of air through vocal tract (above the glottis)
Create a source of sound at the constriction (e.g., release bursts, turbulence)
Voicing may be difficult
Note: this is a phonological distinction, not a phonetic one.

10. Obstruents and Sonorants
Phonologically speaking, there are also different kinds of consonants.
One important distinction is between obstruents and sonorants.
Obstruents
Stops, fricatives, affricates
Obstruct flow of air through the vocal tract so much that voicing is difficult
Sonorants
Nasals, approximants (glides, liquids), trills, flaps
Allow air to flow freely through vocal tract so that resonance (voicing) is still possible

11. Stop Acoustics Overview
Stages of Stop Production
Closing
Closure
Release
Opening
Acoustic Cues for Place of Articulation
Formant transition out of vowel
Closure voicing {or nothing}
Release burst
Formant transition into vowel

12. Release Bursts
The acoustic characteristics of a stop release burst tend to resemble those of a fricative made at the same place of articulation.
Ex: labial release bursts have a very diffuse spectrum, just like bilabial and labio-dental fricatives.
[p] burst

13. Release Bursts: [t]
Alveolar release bursts tend to lack acoustic energy at the bottom of the spectrum.
To some extent, higher frequency components are more intense.
[t] burst

14. Release Bursts: [k] Velar release bursts are relatively intense.
They also often have a strong concentration of energy in the Hz range (F2/F3).
There can often be multiple [k] release bursts.
[k] burst

15. Closure Voicing
During the stop closure phase, only low frequency information escapes from the vocal tract (for voiced stops)
“voicing bar” in spectrogram
analogy: loud music from the next apartment
Armenian:
[bag]
top murmur is [b]
bottom murmur is [g]
This acoustic information provides hardly any cues to place of articulation.

16. [bag] vs. [bak] From Armenian (another language from the Caucasus)
[bag] [bak]

17. Formant Transitions
The resonant frequencies of the vocal tract change as stop gestures enter or exit the closure phase.
Ex: Formant frequencies usually decrease in making the transition from bilabial stop to vowel (or vice versa)

18. Formant Transitions: alveolars
For other places of articulation, the type of formant transition that appears is more complex.
From front vowels into alveolars, F2 tends to slope downward.
From back vowels into alveolars, F2 tends to slope upwards.

19. [hid]
[hæd]

21. Formant Locus Whether in a front vowel or back vowel context...
The formant transitions for alveolars tend to point to the same frequency value. ( Hz)
This (apparent) frequency value is known as the locus of the formant transition.
According to one theory of perception...
the locus frequency can be used by listeners to reliably identify place of articulation.
dog, gob, bod

22. Velar Transitions
Velar formant transitions do not always have a reliable locus frequency for F2.
Velars exhibit a lot of coarticulation with neighboring vowels.
Fronter (more palatal) next to front vowels
Locus is high:  Hz
Backer (more velar) next to back vowels
Locus is lower: < 1500 Hz
F2 and F3 often come together in velar transitions
“Velar Pinch”

23. The Velar Pinch
[bag] [bak]

25. Fricative Transitions
You get transition cues for fricatives at different places of articulation, too.

26. Transitions American : tongue tip between teeth British :
tongue tip behind upper teeth
has a little bit of a transition cue

27. [f] = ?
Labio-dental and interdental fricatives are the most confusable consonants in English.
In some dialects of English, may be replaced by [f].
“with”
“mouth”
Stephen Fry transcription
May be distinguished visually: check out the clips.
E.1
E.5
E.2

28. Approximants
Approximants = one articulator is close to another, but without producing audible turbulence.
They come in two flavors:
Glides (English [w], [j])
Liquids (English , [l])
This distinction is also phonological…
Glides are essentially high-vowel articulations which are not in a syllabic peak.
In English, liquids may form syllables (or syllable peaks).

29. Glides Each glide corresponds to a different high vowel.
Vowel Glide Place
[i] [j] palatal (front, unrounded)
[u] [w] labio-velar (back, rounded)
[y] labial-palatal (front, rounded)
velar (back, unrounded)

30. Glide Examples
French contrasts palatal, labio-palatal and labio-velar glides:
Japanese has velar vowels, but not necessarily velar glides...

31. Glide Acoustics Glides are shorter than vowels
They also tend to lack “steady states”
and exhibit rapid transitions into (or from) vowels
hence: “glides”
Also: lower in intensity
especially in the higher formants

32. [j] vs. [i]

33. [w] vs. [u]

34. Vowel-Glide-Vowel
[iji] [uwu]

35. More Glides
[wi:]
[ju:]