introduction to velopharyngeal function and...

Introduction to Velopharyngeal Function and Dysfunction

Xiaochuan [email protected]

Center for Spoken Language UnderstandingOGI School of Science and EngineeringOregon Health and Science University

CSLU Xiaochuan NiuAugust 24, 2006

Slide 2

Outline

Introduction

Background

Reviews

Our work

Summary


Slide 3

IntroductionTopic:

Velopharyngeal function and dysfunction

Velopharyngeal (VP) portPhysiological structure >

StatusOpening/ClosureIntermediate positions

nasal tract

oral tract

pharyngeal tract glottal folds

velum

rear pharyngeal wall


Slide 4

IntroductionVelopharyngeal function in normal speech

Appropriate opening of the velopharyngeal (VP) port during nasal consonants (/m n ng/), nasal vowels (in French etc.), nasalized phonemes (due to coarticulation)

Appropriate closure of the VP port during “oral” phonemes, such as plosives and fricatives

What is an appropriate VP function?Right timing and right degree


Slide 5

IntroductionVelopharyngeal dysfunction (VPD) in disordered speech [Witt & Rapley 06]

VP insufficiency: the tissue to accomplish closure of the VP port is insufficient (e.g. cleft palate)

VP incompetence: due to neurological etiologies such as motor disorders (e.g dysarthria)

VP incorrect learning: the result of sensory deficits (e.g. hearing impairment), or congenital disorders (existing at birth)


Slide 6

IntroductionMultiple clinical goals of speech pathology

Differential diagnosis to identify the disease or reason causing the dysfunction

Measurement of speech mechanisms to assess the severity of the dysfunction or the disease

Development of approaches to intervention (behavioral, prosthetic or surgical)

Design of the strategy to reduce or stabilize the disability


Slide 7

IntroductionRelated goals of the research on speech science and technology

To understand the mechanism of both the normal and abnormal speech process

To provide technical batteries for diagnosis, assessment, and rehabilitation of disordered speech

These general goals are applicable for the research on VP function and dysfunction


Slide 8

IntroductionGoals of this talk

To introduce the background knowledge of speech physiology and speech production in order to understand the complexity of VP function during speech

To review some measurement techniques used in the study of VP dysfunction and some research aspects on the production model of nasalization

To present our research work related to VP function


Slide 9

Outline

Introduction

Background

Reviews

Our work

Summary


Slide 10

BackgroundCoordinating components of speech production

Respiration: to provide subglottal air pressure

Phonation: to keep tension of vocal folds

Resonance: to open or close nasal and oral cavities

Articulation: to move and shape articulators (tongue, lips, teeth)

Prosody: to convey stress and intonation

VP function affects resonance & interacts with others


Slide 11

BackgroundVP movements during speech

Xray filmsSample #1 (male) & Sample #2 (female)

Endoscopic video in the nasal cavityVelum view & Port view

Combined movements of the velum, rear pharyngeal wall and lateral pharyngeal wall (involving many muscles)

Speaker dependent patterns of movements


Slide 12

BackgroundThe action and location of VP muscles [Laver 80]

1. Soft palate

2. Tongue

3. Thyroid cartilage

4. Palatoglossus muscle

5. Palatopharyngeus muscle

6. Palatal tensor muscle

7. Palatal levator muscle

8. Azygous uvulae muscle

9. Hamular process of the pterygoid bone


Slide 13

BackgroundTerms used in the study of VP function/dysfunction

Nasalization: significant communication of the nasal cavity with the rest of the vocal tract during speech

Nasality: perceptual quality of nasal resonance

Hypernasality: excessive nasally escaping air reverberating in the nasal cavity

Hyponasality: blocked nasal resonance caused by nasal obstruction

Nasal emission: increased nasal instead of oral airflow during the production of pressure consonants (not necessarily acoustic)

Nasal turbulence: fricative sounds caused by nasal airflow


Slide 14

BackgroundResearch and clinical challenges

The position of the VP port is “hidden”It's hard to measure the movement

The perception of nasality is affected by factors besides VP opening

tongue posture / pith and intensity / voice quality

Timing pattern is complex (due to coarticulation)It's almost impossible to discriminate mistiming by listening to the running speech


Slide 15

OutlineIntroduction

Background

ReviewsInstrumental techniques

Acoustics of nasalization

Our work

Summary


Slide 16

Reviews Instrumental techniquesInstrumental techniques [Krakow & Huffman 93, Baken & Orlikoff 00]

Sources of movements

Muscle activities

Movements

ImagingTracking

Effects of movements

Aerodynamic & acoustic consequences


Slide 17

Reviews Instrumental techniquesMuscle activities:

Electromyography (EMG)Surface electrodesIntramuscular electrodes

VP study usually needs the intramuscular ones:

Invasive( Surface EMG )


Slide 18

Reviews Instrumental techniquesImaging

Fiberoptic endoscope

Xray / MRI / Ultrasound

Endoscope: stability

Xray: health risk

MRI: 21ms/frame( MRI: /p a s i/ )


Slide 19

Reviews Instrumental techniquesTracking

Point tracking Radiography (pellets) Magnetometry (coils)

Aperture trackingMechanical

VelotraceStrain gauge

Photodetection (eg. Nasograph)( Magnetmometry )


Slide 20

Reviews Instrumental techniquesAerodynamic & acoustic consequences

AirflowPneumotachograph: split mask with airflow sensors

Sound pressureMicrophones (eg. Probemic, Nasometer)Accelerometers or contact microphones for tissue vibrations


Slide 21

Reviews Instrumental techniquesSummary of instrumental techniques

Research vs. clinical measurement (different goals)

Aspects of practical considerationsInvasiveness / discomfort / health risk / ease of use / time consumed / potability / expense / inherent advantage and limitation / available analysis methods

No “gold standard”: no single measure answer all clinical questions


Slide 22

OutlineIntroduction

Background

ReviewsInstrumental techniques

Acoustics of nasalization

Our work

Summary


Slide 23

Reviews Acoustics of nasalizationResearch on acoustics of nasalization

Speech recognitionAcoustic correlates to nasalization (spectral features)

Speech synthesis / simulationProduction models of nasalization (articulatory or parametric)

Speech analysisModels and algorithms considering the nasal tract for accurate inverse filtering analysis


Slide 24

Reviews Acoustics of nasalizationSome spectral features of nasalization

Reduction in amplitude of the first formant [Fant 60, House & Stevens 56]

Introduction of a polezero pair in the region of the first formant [House & Stevens 56, Maeda 82, Huffman 90]

Extra nasal resonance between 250 and 450Hz [Maeda 82]

Distance between the two spectral peaks in low frequency range [Maeda 93, Chen 97]


Slide 25

Reviews Acoustics of nasalizationProduction models of nasalization

Parametric synthesis [Hawkins & Stevens 85]Sourcefilter model with polezero pair

Articulatory simulation [Maeda 82]Transmissionline model with the extension of nasaltract area function

The production models are useful tools to test hypotheses of the relation between the production and perception of nasalized sounds


Slide 26

Reviews Acoustics of nasalizationAnalysis models and algorithms with the nasal tract assumption

ARMR model of the vocal filter and algorithms to estimate its parameters [Fujisaki & Ljungqvist 87, Liu & Lacroix 96]

Branched vocal tract, lossless tube model [Lim & Lee 93, Schell & Lacroix 02]


Slide 27

Reviews Acoustics of nasalizationSummary of the research on acoustics of nasalization

Focus on the production mechanism or characteristics of normal nasals and nasalized vowels

The analysis target is simply the sound power signal without other additional information


Slide 28

OutlineIntroduction

Background

Reviews

Our workAn airflow device

Dual channel acoustic analysis

Summary


Slide 29

Our work – An airflow deviceMotivations

Simultaneously recording both nasal airflow and acoustic signals without interference with articulation and degradation of the acoustic signal

Device designBernoulli's equation

Pt1=Ps12V2

Pt2=Ps−12V2

Ps Pt1 Pt2

flow


Slide 30

Our work – An airflow device

Data acquisition of DC signals with a sound card:Differential pressure sensor

Processing modules: power supply, offset and gain control, and frequency modulation (FM)


Slide 31

Our work – An airflow deviceDemodulation algorithm

Sampling & lowpass filtering (5kHz)

Discrete Hilbert transform to obtain the analytical signal

Get phase signal by canceling the carrier frequency

Compute the derivative of the phase signal


Slide 32

Our work – An airflow deviceAcoustic, demodulated nasal airflow, and static airflow


Slide 33

Our work – An airflow deviceObservations:

The demodulated airflow signal contain strong harmonic components during the sections of voiced speech sounds;

The filtered DC and lowfrequency components represents the static airflow as it moves in and out of the nostril;

The static nasal airflow peaks occur ...


Slide 34

Our work – An airflow deviceSummary

A quantitative measurement of the static nasal airflow

Nonspeech information, such as inhalation and exhalation

VP information about the detailed timecourse of nasal, nasalized vowel, and nasal emission events during normal speech

Potable, lowcost, less interference with the articulatory process during speech


Slide 35

OutlineIntroduction

Background

Reviews

Our workAn airflow device

Dual channel acoustic analysis

Summary


Slide 36

Our work – Dual channel acoustic analysis

MotivationsTo make full usage of the information from two acoustic channels (with a device like the Nasometer)

To study the relationship between the nasal and oral acoustic signals during nasalization

To derive acoustic features of nasalization from the dual channel analysis


Slide 37


Theoretical formulation – transmission line model

po

v

pp

pp

pi

g

U

P

DC

BA=

U

P

mo

ml

mm

mm

mi

v

U

P

DC

BA=

U

P

=

no

nl

nn

nn

ni

v

U

P

DC

BA

U

P

[Flanagan 72]


Slide 38


Theoretical formulationTransfer ratio function of the volume velocity from lips to nostrils

T n /m ≝U no

U mo

=Am Z mlBm

An Z nlBn

PropertiesIndependent on the acoustic system below the velumAll poles of the transfer ratio function stem from transfer admittance function of the nasal cavity


Slide 39


Analysis methodAssuming the transfer ratio function in the Zdomain has the following form

The parameters are estimation by minimizing the mean square error of the following system

Tn /m

Z =Uno Z

Umo Z =

b0b1 Z−1⋯bN Z N

1a1 Z−1⋯aM Z M


Slide 40


Articulatory simulationTo test the analysis method against the synthesized nasalized signals


Slide 41


ResultsThe estimated transfer ratio function matches the preset parameters

The polezero pattern of the transfer ration function mainly reflects the property of the nasal tract and the velum opening


Slide 42


SummaryThe analysis method provides a new way to nasalization measurement

Our further work will includeApplying the method to dual channel recorded dataDeveloping and test the acoustic feature of nasalization from this approachDeveloping the method into an assessment tool for VP dysfunction


Slide 43

Outline

Introduction

Background

Reviews

Our work

Summary


Slide 44

SummaryUnderstanding the complexity of VP function during speech

Standing on the bridge between speech pathology and speech technology


Slide 45

ReferenceBaken, R.J. & Orlikoff, R.F (2000), Clinical Measurement of Speech and Voice, 2nd edition, Thomson, Delmar Learning.

Chen, M.Y (1997), “Acoustic Correlates of English and French Nasalized Vowels,” J. Acoust. Soc. Am. 102 (4), pp 23602370.

Fant, G. (1960), The Acoustic Theory of Speech Production, Mouton, The Hague.

Flanagan, J.L. (1972), Speech Analysis Synthesis and Perception, 2nd edition, SpringerVerlag

Fujisaki, H. & Ljungqvist, M. (1987), “Estimation of Voice Source and Vocal Tract Parameters Based on ARMA Analysis and a Model for the Glottal Source Waveform,” Proc. IEEE Int. Conf. ASSP 12, pp 637640.

Hawkins, S. & Stevens, K.N. (1985), “Acoustic and Perceptual Correlates of the NonnasalNasal Distinction for Vowels,” J. Acoust. Soc. Am. 77, pp 15601575.

House, A.S. & Stevens, K.N. (1956), “Analog Study of the Nasalization of Vowels,” J. Speech Hear. Dis. 21, pp 218232.


Slide 46

ReferenceHuffman, M. (1990), “Implementation of Nasal: Timing and Articulatory Landmarks,” UCLA Working Papers in Phonetics 75, pp 112143.

Krakow, R.A., & Huffman, M.K. (1993), “Instruments and Techniques for Investigating Nasalization and Velopharyngeal Function in the Laboratory: An Introduction,” in Phonetics and Phonology Volume 5: Nasals, Nasalization and the Velum, edited by M. K. Huffman and R. A. Krakow, Academic, New York, pp359.

Laver, J. (1980), The Phonetic Description of Voice Quality, Cambridge University Press, pp 6892.

Lim, IT. & Lee, B.G. (1993), “Lossless polezero modeling of speech signals,” Trans. IEEE SAP, pp 269276

Liu, M. & Lacroix, A. (1996), “Improved Vocal Tract Model for the Analysis of Nasal Speech Sounds,” Proc. IEEE Int. Conf. ASSP, pp 801804.

Maeda, S. (1982), “The Role of the Sinus Cavities in the Production of Nasal Vowels,” Proc. IEEE Int. Conf. ASSP 2, pp 911914.


Slide 47

ReferenceMaeda, S. (1993), “Acoustic of Vowel Nasalization and Articulatory Shifts in French Nasal Vowels,” in Phonetics and Phonology Volume 5: Nasals, Nasalization and the Velum, edited by M. K. Huffman and R. A. Krakow, Academic, New York, pp 147167.

Schell, K. & Lacroix, A. (2002), “Parameter Estimation of Branched Tube Models by Iterative Inverse Filtering”, Proc. IEEE Int. Conf. DSP, pp 333336.

Witt, P. & Rapley, J. (2006), “Craniofacial, Postpalatoplasty Speech Dysfunction,” eMedicine Specialties.

Website (for some videos and figures in the slides):

http://www.shlrc.mq.edu.au/speech/resources.html

http://www.phonetik.unimuenchen.de/indexeng.html

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