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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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Nasal StopsNasal Stops
NasalsNasals
Distinct vocal tract configurationDistinct vocal tract configuration
Pharyngeal cavity
Oral cavity (closed)
Nasal cavity (open)
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
Bilabial /m/ Alveolar /n/ Velar / /
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’
Clinical DiversionClinical Diversion
Measuring velopharyngeal functionMeasuring velopharyngeal function– Visualization: nasendoscopyVisualization: nasendoscopy– Aerodynamic: oral-nasal airflowAerodynamic: oral-nasal airflow– Acoustic: NasometryAcoustic: Nasometry
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
Example from LiteratureExample from Literature
From Skinder-Meredith, Carkoski, Graf (2004)
Childhood apraxiaRepaired cleftTypically developing
Oral Stops/PlosivesOral Stops/Plosives
Aerodynamic SequenceAerodynamic Sequence
time
vowel plosive vowel
Intr
aora
l Pre
ssur
e O
ral a
irflo
w
S
ound
Pre
ssur
e
Acoustic SequenceAcoustic Sequence
vowel vowel
releaseburst
silent gap/closure interval
voice onset time
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
QuestionQuestion
How can voicing continue with How can voicing continue with a closed vocal tract?a closed vocal tract?
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
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)
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
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
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
(Azou et al., 2000)(Azou et al., 2000)
Voice onset time has been Voice onset time has been considered an important considered an important
measure of coordination. Why?measure of coordination. Why?
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
Formant transitions: bilabialFormant transitions: bilabial
ahb
Formant transitions: alveolarFormant transitions: alveolar
ahd
Formant transitions: velarFormant transitions: velar
ahg
Formant transition: voiced vs. voicelessFormant transition: voiced vs. voiceless
voiceless
voiced
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
(Azou et al., 2000)(Azou et al., 2000)