Nasal stops
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Nasal Stops. Nasals. Distinct vocal tract configuration. Nasal cavity (open). Oral cavity (closed). Pharyngeal cavity. Features of nasals. Vocal tract longer than for oral sounds ↓ resonant (formant) frequencies Nasal formant/murmur Nasal cavity is acoustically absorbent

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Nasal Stops

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Nasal stops

Nasal Stops


Nasals

Nasals

  • Distinct vocal tract configuration

Nasal cavity (open)

Oral cavity (closed)

Pharyngeal cavity


Features of nasals

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


Nasal stops

  • Bilabial /m/ Alveolar /n/ Velar / /


Formant transitions

Formant Transitions

Bilabial

  • F1: very low

  • F2: ~ 600-800 Hz

    Alveolar

  • F1: very low

  • F2: ~ 1800 Hz

    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’


Oral stops plosives

Oral Stops/Plosives


Aerodynamic sequence

Aerodynamic Sequence

vowel plosive vowel

Intraoral Pressure Oral airflow Sound Pressure

time


Acoustic sequence

Acoustic Sequence

voice onset time

release

burst

silent gap/

closure interval

vowel

vowel


Silent gap closure interval

What is it?

Period during VT occlusion

Voiceless:

relatively long

Voiced:

reduced or absent closure interval

May exhibit a “voice bar”

Silent gap/closure interval

voiceless

voiced

voice bar


Question

Question

How can voicing continue with a closed vocal tract?


Release burst

What is it?

Acoustic energy associated with VT release

Transient:

~10-30 msec

Aperiodic

Often absent in final position

Release burst


Release burst1

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 ~500-1500 Hz

  • Alveolar:

    • diffuse energy that is dominant in higher frequencies (>4000 Hz)

  • Velar:

    • compact energy in midrange (1500-4000 Hz)


Aspiration

Aspiration

  • Observed in voiceless stops

  • Consequence of air turbulence at the open glottis

  • Increases the duration of the release burst


Voice onset time

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

Voice onset time

voiceless

voiced


Voice onset time1

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


Nasal stops

(Azou et al., 2000)


Voice onset time has been considered an important measure of coordination why

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


Formant transitions1

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


Formant transitions bilabial

Formant transitions: bilabial

b

ah


Formant transitions alveolar

Formant transitions: alveolar

d

ah


Formant transitions velar

Formant transitions: velar

g

ah


Formant transition voiced vs voiceless

Formant transition: voiced vs. voiceless

voiceless

voiced


Vot and clinical populations azou et al 2000

VOT and clinical populations (Azou et al., 2000)

  • Aphasia

    • phonetic vs. phonemic errors

  • Apraxia & dysarthria

    • Marking, place, voicing and manner

    • Variability of productions


Nasal stops

(Azou et al., 2000)


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