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Nasal Stops.

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Presentation on theme: "Nasal Stops."— Presentation transcript:

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: bilabial

20 Formant transitions: alveolar
d ah

21 Formant transitions: velar
g 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)

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