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 ratio
4. perturbation measures
5. 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
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EGG
Electrodes
Glottis
Electroglottograph
electronics
Vocal fold
contact area
• Lines between electrodes represent the
electrical current traversing through the v.f.’s6
EGG Signal (inverse filtered)
1000
Airflow
68 MSEC
EGG
• Opening (upward trace); Closing (downward
trace)
• v.f.’s touch (close) = greater current
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Width of area of glottis
(% of Maximum)
OPEN
Point of max opening
Glottogram
CLOSED
Opening
Closing
Open Phase
1 Cycle (T)
Closed Phase
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EGG: Normal & Disordered Glottal Waves
Midline
Left Vocal fold
Midline
Relative distance from midline
Right Vocal fold
B.
Left Vocal fold
Relative distance from midline
A.
Right Vocal fold
A. Normal glottal width function
Time of frame number
B. Left recurrent nerve paralysis (Left never reaches midline
& greater excursion; right fold crosses midline)
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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
Vowel Production
Voice
CT
Long relaxation time
CV Combos
Voice
CT
Buildup of EMG activity in CT
ba
ba
ba
bababa
da
da
dadada
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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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A. Increased in subglottal pressure
to overcome increase in glottal
resistance
B. Larynx offers increased resistance
to airflow as folds are placed under
increased tension
Glottal resistance (dynes/se/cm)
Intratracheal Pressure (cm H20)
Glottal Resistance
Fundamental Frequency (% of Freq. range)
Fundamental Frequency (% of Freq. range)
*30% of F0= Most efficient function of the larynx or habitual pitch
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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 severity
3. Suggest implications for the diagnostic
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source of voice pathology
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)
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