1. Voice Onset Time + Voice Quality
November 28, 2011

2. The Future Production Exercise #3 is due.
This week: the basics of obstruent acoustics
On Wednesday: cues for place of articulation.
On Friday: more spectrogram matching.
Next week: sonorant acoustics
approximants and nasals
Production Exercise #4 for Wednesday the 7th.

3. Review: Stops and Voicing
Three stages: close, maintain, release
Pressure build-up behind closure
“Release Burst”
Voicing
Vocal folds are lightly brought together (adducted)
Sub-glottal pressure higher than supra-glottal pressure
Airflow through glottis causes cycle of vocal fold opening and closing
Voiceless: k > t > p Voiced: b > d > g

4. It’s not that simple
The voicing of stops is difficult, so the contrast between voiced and voiceless stops often takes a different form
Making use of a different property: aspiration
An aspirated stop has the following timing:
Stop closure is made
Airflow builds up pressure behind closure
Closure is released (with a “burst”)
Air flows unimpeded through glottis (“aspiration”)
Vocal folds close; voicing begins

5. An Aspirated Stop: [phœt]
aspiration
release burst
[t] release burst
voicing (vowel)
[t] closure

6. An Unaspirated Stop: [pœt]
voicing (vowel)
release burst

7. A Voiced Stop: [byt]
release burst
voicing (closure)
voicing (vowel)

8. Voice Onset Time
Voice Onset Time (VOT) is defined as the length of time between the release of a stop closure and the onset of voicing.
For aspirated stops--voicing begins after the release, so:
VOT  milliseconds
For unaspirated stops--voicing begins at the release, so:
VOT  milliseconds
For voiced stops--voicing begins before the release, so:
VOT < 0 milliseconds
(VOT can be negative)

9. Thai Stops In stressed onset position, English distinguishes between:
unaspirated and aspirated stops.
Languages like French, Dutch and Spanish distinguish between:
voiced and voiceless unaspirated stops.
Thai splits up the VOT continuum into three parts:
voiced, voiceless unaspirated, voiceless aspirated

10. Thai Stops

11. [ba]
[pa]

12. English Stop Contrasts
In onset position:
/p/ is voiceless aspirated
/b/ is voiceless unaspirated
In medial position (between voiced segments):
/p/ is voiceless unaspirated
/b/ is voiced
After /s/, in the same syllable:
only voiceless unaspirated stops (no contrast)

13. Beak, Peak, Speak

14. Rabid vs. Rapid

15. English Stop Contrasts
4. In syllable-final position:
vowels preceding /p/ are short
vowels preceding /b/ are longer
/p/ closure tends to be longer than /b/ closure
Moral of the story:
Phonological voiced vs. voiceless contrast in English is abstract
It may exhibit different phonetic manifestations
Phonemes vs. Allophones

16. Complication #1 Fricatives and affricates may also be aspirated
In these cases, VOT must be calculated beginning from the offset of sibilance.

18. Tree vs. Chree
Check ‘em out in Praat

19. Syllable-Final
Syllable-final obstruents may also be distinguished by aspiration.
Examples from Armenian
In this case, voicing does not necessarily resume after aspiration

20. Syllable-Final Spectrograms
release burst
aspiration

21. Practical Point: Pop Filters
When recording speech digitally, the airflow of aspiration can cause “pops” to appear in the recording.
A result of clipping the waveform
If you have some extra cash, this problem can be solved by placing a pop filter in front of the microphone.
Otherwise, make sure the microphone is not directly in front of the speaker’s lips.

22. Voice Quality
Note that there are three primary types of vocal fold vibration:
modal
vocal folds lightly adducted; flow of air causes periodic opening and closing of folds (“trilling”)
breathy
vocal folds slightly apart; flow of air makes folds “wave” in the wind
creaky
vocal folds tensely adducted; low airflow causes irregular, low frequency voicing

23. breathy
[ ]
creaky

24. Modal to Creaky
[ ]

25. Voice Quality Movies
Source:

26. Contrasts
Gujarati contrasts breathy voiced vowels with modal voiced vowels:
Jalapa Mazatec has a three-way contrast between modal, breathy and creaky voiced vowels:

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

28. [phal]