nasal stops

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Nasal Stops 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 - PowerPoint PPT Presentation

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Page 1: Nasal Stops

Nasal StopsNasal Stops

Page 2: Nasal Stops

NasalsNasals

Distinct vocal tract configurationDistinct vocal tract configuration

Pharyngeal cavity

Oral cavity (closed)

Nasal cavity (open)

Page 3: Nasal Stops

Features of nasalsFeatures of nasals

Vocal tract longer than for oral soundsVocal tract longer than for oral sounds– ↓ ↓ resonant (formant) frequenciesresonant (formant) frequencies– Nasal formant/murmurNasal formant/murmur

Nasal cavity is acoustically absorbentNasal cavity is acoustically absorbent– Attenuates overall energyAttenuates overall energy– Acts as a low-pass filterActs as a low-pass filter

Pharyngeal/oral cavity acts as a “cul-de-sac”Pharyngeal/oral cavity acts as a “cul-de-sac”– Introduces antiresonances/antiformantsIntroduces antiresonances/antiformants

Formant transitionsFormant transitions– Varies for place of articulationVaries for place of articulation

Page 4: Nasal Stops

Bilabial /m/ Alveolar /n/ Velar / /

Page 5: Nasal Stops

Formant TransitionsFormant TransitionsBilabialBilabial

F1: very lowF1: very lowF2: ~ 600-800 HzF2: ~ 600-800 Hz

AlveolarAlveolarF1: very lowF1: very lowF2: ~ 1800 HzF2: ~ 1800 Hz

VelarVelarF1: very lowF1: very lowF2: F2: – Adjacent to back vowel ~ 1300 HzAdjacent to back vowel ~ 1300 Hz– Adjacent to front vowel ~ 2300 Hz Adjacent to front vowel ~ 2300 Hz

F3: F3: – near F2near F2– F2-F3 transition is ‘wedge-shaped’F2-F3 transition is ‘wedge-shaped’

Page 6: Nasal Stops

Clinical DiversionClinical Diversion

Measuring velopharyngeal functionMeasuring velopharyngeal function– Visualization: nasendoscopyVisualization: nasendoscopy– Aerodynamic: oral-nasal airflowAerodynamic: oral-nasal airflow– Acoustic: NasometryAcoustic: Nasometry

Page 7: Nasal Stops

NasometerNasometer

Two microphonesTwo microphones– OralOral– NasalNasal– Separated by solid Separated by solid

plateplate

Nasalence: Nasalence: – Nasal/oral energyNasal/oral energy

ApplicationApplication– Variety of “nasal Variety of “nasal

resonance” disordersresonance” disorders

Page 8: Nasal Stops

Example from LiteratureExample from Literature

From Skinder-Meredith, Carkoski, Graf (2004)

Childhood apraxiaRepaired cleftTypically developing

Page 9: Nasal Stops

Oral Stops/PlosivesOral Stops/Plosives

Page 10: Nasal Stops

Aerodynamic SequenceAerodynamic Sequence

time

vowel plosive vowel

Intr

aora

l Pre

ssur

e O

ral a

irflo

w

S

ound

Pre

ssur

e

Page 11: Nasal Stops

Acoustic SequenceAcoustic Sequence

vowel vowel

releaseburst

silent gap/closure interval

voice onset time

Page 12: Nasal Stops

Silent gap/closure intervalSilent gap/closure interval

What is it?What is it?

Period during VT occlusionPeriod during VT occlusion

Voiceless: Voiceless:

relatively longrelatively long

Voiced:Voiced:

reduced or absent closure reduced or absent closure intervalinterval

May exhibit a “voice bar”May exhibit a “voice bar”

voiceless

voiced voice bar

Page 13: Nasal Stops

QuestionQuestion

How can voicing continue with How can voicing continue with a closed vocal tract?a closed vocal tract?

Page 14: Nasal Stops

Release burstRelease burst

What is it?What is it?Acoustic energy Acoustic energy associated with VT associated with VT releaserelease

Transient: Transient: – ~10-30 msec~10-30 msec

Aperiodic Aperiodic Often absent in final Often absent in final positionposition

Page 15: Nasal Stops

Release burstRelease burst

Provides place informationProvides place informationSpectral shape related to cavity size in front of constrictionSpectral shape related to cavity size in front of constriction

Bilabial: Bilabial: – diffuse energy dominant in low frequency diffuse energy dominant in low frequency – Either gently sloping spectrum or ~500-1500 HzEither gently sloping spectrum or ~500-1500 Hz

Alveolar: Alveolar: – diffuse energy that is dominant in higher frequencies (>4000 Hz)diffuse energy that is dominant in higher frequencies (>4000 Hz)

Velar: Velar: – compact energy in midrange (1500-4000 Hz)compact energy in midrange (1500-4000 Hz)

Page 16: Nasal Stops

AspirationAspiration

Observed in voiceless stopsObserved in voiceless stops

Consequence of air turbulence at the open Consequence of air turbulence at the open glottisglottis

Increases the duration of the release burstIncreases the duration of the release burst

Page 17: Nasal Stops

Voice onset timeVoice onset time

VoicelessVoicelessTermed long lag VOTTermed long lag VOTVOT ranges from 25 – 100 msecVOT ranges from 25 – 100 msec

VoicedVoicedShort lag: Short lag: – Voice onset shortly after releaseVoice onset shortly after release– VOT>0VOT>0

Simultaneous voicing: Simultaneous voicing: – voicing and release are coincidentvoicing and release are coincident– VOT = 0VOT = 0

Prevoicing/VOT lead: Prevoicing/VOT lead: – voicing occurs before releasevoicing occurs before release– VOT <0VOT <0

VOT ranges from –20 – 20 msecVOT ranges from –20 – 20 msec

voiceless

voiced

Page 18: Nasal Stops

Voice onset timeVoice onset time

VOT may distinguish place of articulationVOT may distinguish place of articulation

Bilabial: relatively short VOTBilabial: relatively short VOT

Alveolar: mid-length VOTAlveolar: mid-length VOT

Velar: relatively long VOTVelar: relatively long VOT

RULE: as the cavity in front of the RULE: as the cavity in front of the occlusion gets longer, VOT increasesocclusion gets longer, VOT increases

Page 19: Nasal Stops

(Azou et al., 2000)(Azou et al., 2000)

Page 20: Nasal Stops

Voice onset time has been Voice onset time has been considered an important considered an important

measure of coordination. Why?measure of coordination. Why?

Page 21: Nasal Stops

Formant TransitionsFormant Transitions

Formants of adjacent vowels will change with VT Formants of adjacent vowels will change with VT occlusionocclusionTransitions will last about 50 msec (shorter than Transitions will last about 50 msec (shorter than glides/liquids)glides/liquids)Transitions not obvious with voicelessTransitions not obvious with voicelessThe form of the transition is a function of The form of the transition is a function of – The place of articulationThe place of articulation– The neighboring soundThe neighboring sound– F1 and F2 are the key playersF1 and F2 are the key players

Page 22: Nasal Stops

Formant transitions: bilabialFormant transitions: bilabial

ahb

Page 23: Nasal Stops

Formant transitions: alveolarFormant transitions: alveolar

ahd

Page 24: Nasal Stops

Formant transitions: velarFormant transitions: velar

ahg

Page 25: Nasal Stops

Formant transition: voiced vs. voicelessFormant transition: voiced vs. voiceless

voiceless

voiced

Page 26: Nasal Stops

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

AphasiaAphasia– phonetic vs. phonemic errorsphonetic vs. phonemic errors

Apraxia & dysarthriaApraxia & dysarthria– Marking, place, voicing and mannerMarking, place, voicing and manner– Variability of productions Variability of productions

Page 27: Nasal Stops

(Azou et al., 2000)(Azou et al., 2000)