1. Nasal Stops

2. Nasals Distinct vocal tract configuration Nasal cavity (open)
Oral cavity (closed)
Pharyngeal cavity

3. Features of nasals Vocal tract longer than for oral sounds
↓ resonant (formant) frequencies
Nasal formant/murmur
Nasal cavity is acoustically absorbent
Attenuates overall energy
Acts as a low-pass filter
Pharyngeal/oral cavity acts as a “cul-de-sac”
Introduces antiresonances/antiformants
Formant transitions
Varies for place of articulation

4. Bilabial /m/ Alveolar /n/ Velar /  /

5. Formant Transitions Bilabial F1: very low F2: ~ 600-800 Hz Alveolar
Velar
F1: very low
F2:
Adjacent to back vowel ~ 1300 Hz
Adjacent to front vowel ~ 2300 Hz
F3:
near F2
F2-F3 transition is ‘wedge-shaped’

6. Oral Stops/Plosives

7. Aerodynamic Sequence vowel plosive vowel time
Intraoral Pressure Oral airflow Sound Pressure
time

8. Acoustic Sequence voice onset time release burst silent gap/
closure interval
vowel
vowel

9. Silent gap/closure interval
voiceless
What is it?
Period during VT occlusion
Voiceless:
relatively long
Voiced:
reduced or absent closure interval
May exhibit a “voice bar”
voiced
voice bar

10. How can voicing continue with a closed vocal tract?
Question
How can voicing continue with a closed vocal tract?

11. Release burst What is it? Acoustic energy associated with VT release
Transient:
~10-30 msec
Aperiodic
Often absent in final position

12. Release burst Provides place information
Spectral shape related to cavity size in front of constriction
Bilabial:
diffuse energy dominant in low frequency
Either gently sloping spectrum or ~ Hz
Alveolar:
diffuse energy that is dominant in higher frequencies (>4000 Hz)
Velar:
compact energy in midrange ( Hz)

13. Aspiration Observed in voiceless stops
Consequence of air turbulence at the open glottis
Increases the duration of the release burst

14. Voice onset time voiceless voiced Voiceless Termed long lag VOT
VOT ranges from 25 – 100 msec
Voiced
Short lag:
Voice onset shortly after release
VOT>0
Simultaneous voicing:
voicing and release are coincident
VOT = 0
Prevoicing/VOT lead:
voicing occurs before release
VOT <0
VOT ranges from –20 – 20 msec
voiced

15. Voice onset time VOT may distinguish place of articulation
Bilabial: relatively short VOT
Alveolar: mid-length VOT
Velar: relatively long VOT
RULE: as the cavity in front of the occlusion gets longer, VOT increases

16. (Azou et al., 2000)

17. Voice onset time has been considered an important measure of coordination. Why?

18. Formant Transitions
Formants of adjacent vowels will change with VT occlusion
Transitions will last about 50 msec (shorter than glides/liquids)
Transitions not obvious with voiceless
The form of the transition is a function of
The place of articulation
The neighboring sound
F1 and F2 are the key players

19. Formant transitions: bilabialah

20. Formant transitions: alveolard ah

21. Formant transitions: velarg ah

22. Formant transition: voiced vs. voiceless

23. VOT and clinical populations (Azou et al., 2000)
Aphasia
phonetic vs. phonemic errors
Apraxia & dysarthria
Marking, place, voicing and manner
Variability of productions

24. (Azou et al., 2000)