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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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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
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’
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
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
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
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