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Voice Assessment: Instrumental

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Instrumental Analysis of Voice

• Electromyographic assessment: direct measure of muscle activity; used for localization of muscle

• Aerodynamic assessment:

1. airflow rate & volume

2. subglottal (intraoral) pressure

3. laryngeal resistance

4. phonation threshold pressure

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Instrumental Analysis of Voice• Acoustic recording & analysis:

1. fundamental frequency (Fo)2. intensity (dB SPL)3. signal/ noise ratio4. perturbation measures5. spectral frequencies

• Electroglottography: measure of vocal fold contact area

• Photoglottography: measure of glottal area

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Why do instrumentation evaluation?

• Contributes to the diagnosis, etiology and severity of the disorder,

• Allows perceptual measures to be objectified (i.e documentable),

• Instrumental evaluations are “noninvasive”,

• Baseline for documentation of progress,

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Electroglottography

• Noninvasive, inexpensive,

• Demonstrates relative contact of the vocal folds during a glottal cycle,

• No information concerning area of glottal opening,

• Small electrodes on neck; – glottis opens= impedance rises, – glottis closes= impedance falls

6• Lines between electrodes represent the electrical current

traversing through the v.f.’s

Electrodes

Glottis

Vocal fold contact area

Electroglottographelectronics

EGG

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EGG Signal (inverse filtered)

• Opening (upward trace); Closing (downward trace)

• v.f.’s touch (close) = greater current

Airflow

EGG

1000

68 MSEC

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GlottogramPoint of max opening

Opening Closing

OPEN

CLOSED

Wid

th o

f ar

ea o

f gl

otti

s(%

of

Max

imum

)

Open PhaseClosed Phase

1 Cycle (T)

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EGG: Normal & Disordered Glottal Waves

A. Normal glottal width function

B. Left recurrent nerve paralysis (Left never reaches midline & greater excursion; right fold crosses midline)

A. B.

MidlineMidline

Rel

ativ

e d

ista

nce

fro

m m

idli

ne

Lef

t V

ocal

fol

dR

igh

t V

ocal

fol

d

Rel

ativ

e d

ista

nce

fro

m m

idli

ne

Lef

t V

ocal

fol

dR

igh

t V

ocal

fol

d

Time of frame number

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Electromyography• Electrodes are either surface or needle,

• Needle inserted into specific muscles

• What do we look for?

1. onset & offset of muscle activity

2. pattern of muscle activity

4. amplitude of muscle activity

5. spont. bursts of activity

• Useful for voice problems with neurological or neuromuscular etiology.

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EMG: Hooked Wire Electrode

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EMG

Voice

CT

Long relaxation timeVoice

CT

ba ba babababa da da dadada

Buildup of EMG activity in CT

Vowel Production

CV Combos

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Aerodynamic• Define vocal efficiency through airflow

rates & pressure changes,

• Airflow rates: flow of air through the glottis, – measured using pneumotachography & body

plethesmography

• Subglottal pressure: driving pressure underneath the folds, – pitot tube & pressure transducer, tube placed in

the oral cavity, – invasive method = esophageal balloon

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Aerodynamic

• Laryngeal resistance: peak intraoral pressure divided by peak flow rate, reflects the overall resistance of the glottis,

• Phonation threshold pressure: minimal pressure to set v.f.’s into oscillation

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Glottal Resistance

*30% of F0= Most efficient function of the larynx or habitual pitch

Fundamental Frequency (% of Freq. range)

Fundamental Frequency (% of Freq. range)

Intr

atra

chea

l Pre

ssur

e (c

m H

20)

Glo

ttal

res

ista

nce

(dy

nes

/se/

cm)

A. Increased in subglottal pressureto overcome increase in glottal resistance

B. Larynx offers increased resistanceto airflow as folds are placed underincreased tension

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Importance of aerodynamic results?• Results are a reflection of the valving activity of the

larynx,

• Represents v.f. configuration, movement, structure & function,

• Intraoral pressure, transglottal airflow, & laryngeal resistance:

1. Discriminate normal & pathologic voice function,

2. Assess severity3. Suggest implications for the diagnostic

source of voice pathology

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Acoustic• Fundamental frequency: rate of vibration of the vocal folds,

expressed in Hertz, or cycles per second, measure on sustained vowel or connected speech,

– Visipitch, C-Speech, CSL

• Perturbation measures: cycle-to-cycle variation in a signal; jitter (frequency) & Shimmer (amplitude),

– Visipitch, C-Speech, CSL

• Signal to noise ratio: a measure of the energy in the voice signal over the noise energy in the voice signal, greater harmonic energy in voice= better voice quality,

– Visipitch, C-Speech, CSL

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Acoustic

• Intensity: SPL (Sound Pressure Level), measure mean and range intensity, – Sound level meter or acoustic analysis programs

• Spectral analysis: displays glottal sound source & filtered characteristics of the speech signal across time, useful to analyze changes in the spectral characteristics of the voice sound, – C-Speech, CSL

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Spectographs

Aperiodic v.f. vibration is evident by the irregularity of the spacing of the vertical voice bars

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Spectograhs: Voice Quality

Normal Nasal Breathy Harsh Hoarse

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Spectographs: Vocal Nodules

A. Vocal Nodule

B. Aperiodic vocal fold vibration& Noise

C. Six weeks post surgery

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Importance of Acoustic Measures• Provide objective & noninvasive measures of

vocal function

• Normative values help you discriminate normal and pathological voice attributes

• Measure change in vocal performance over time

• Indirect inference about the severity of voice

• No acoustic measures can differentially diagnose the source of the voice pathology

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Case # 1

• 41 year old attorney

• 4 months dysphonia

• Problem began after severe URI– chronic coughing & clearing

• Long history of cigarette smoking ( 1 pack per day)

• Moderate alcohol consumption

• Voice abuser: home, sporting event, work

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Examination Findings

• Mild-moderately hoarse- breathy

• Dramatic pitch decrease (2 months)

• Syllables per breath were normal

• Maximum phonation time = 16 seconds

• Acoustic:– F0= 105 hz

– Jitter = 1.4%

– Shimmer = .33 dB

– S/N ratio = 12.7 dB

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Examination Findings

• Aerodynamic:

– Mean airflow (l/sec)= 798 cc /sec

– Subglottal pressure = 20 cm H20

– Glottal resistence= 20 cm H20/lps

• compressoin force between vocal folds during closed

phase of vibration

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Diagnosis

• Bilateral true vocal fold hemorrhagic polyps– secondary to voice misuse & abuse

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Readings

• Colton & Casper Ch.7 (Last half particularly)