Electroglottography
Lab 7
Electroglottography (EGG)
Transduce impedance changes in the area
between the electrodes
Signal not effected by the vowels being
produced
Transduces the VOCAL FOLD CONTACT
AREA
ONLY information about when the vocal folds
are in contact- nothing about the open phase
(or glottal width)
Electroglottography (EGG)
 Demonstrates vocal fold contact area
 Useful in understanding aspects of vocal fold
vibration- Asses Lx function
 Noninvasive, inexpensive,
 No information concerning area of glottal
opening,
 Small electrodes on neck;
glottis opens= impedance rises,
glottis closes= impedance falls
EGG
Electrodes
Glottis
Electroglottograph
electronics
Vocal fold
contact area
Lines between electrodes represent the electrical
current traversing through the v.f.’s
EGG Signal (inverse filtered)
1000
Airflow
68 MSEC
EGG
Closing (upward trace); Opening (downward
trace)
v.f.’s touch (close) = greater current
Width of area of glottis
(% of Maximum)
Closed
Point of max Closing
Glottogram
Open
Open
Closing
Opening
1 Cycle (T)
EGG Contact
As vocal folds open & close during vibration,
the signal’s intensity changes
Air = bad conductor (shows v.f. abduction)
Tissue= good conductor (little impedance)
The electrodes sense resistance.
Does not measure glottal area but the
amount of tissue in contact with other tissue.
EGG Contact Area
Ventilatory
position
Open Phase
Closed Phase
Different degrees of vocal fold
contact during closed phase
Interpretation of EGG
Waveforms
Graph represents vocal contact area
Graph Interpretation
 A flat Segment 1 represents minimal contact of the
vocal folds. It shows the period during which the vocal
folds are separated, it is during this phase that peak
glottal flow occurs
 During Segment 2 interelctrode impedance falls rapidly,
marking the growing contact of the vocal folds
 Segment 3 is the period of maximal vocal fold contact.
 Vocal fold contact is lost during Segment 4 until a
minimum is again reached, ending the glottal cycle
Laboratory
 Part I: EGG Setup & Electrode Placement:
Place electrodes on thyroid lamina: Label printout
“Thyroid”
Sustain /i /
Place electrodes just below hyoid: Label printout
“Subhyoid”
Sustain /i /
Place electrodes on the cricoid : Label printout
“Cricoid”
Sustain /i /
Summarize effects of electrode placement
Laboratory
Part II: The Lx wave
Place electrodes on thyroid
Adjust gain on CSL (Channel 2)
Sustain /a/and printout records: **can capture 2
waveforms on each printout from view A & B
• Comfortable pitch & loudness
• Somewhat lower pitch & same loudness
• Somewhat higher pitch & same loudness
• Comfortable pitch and softer than comfortable loudness
• Comfortable pitch and greater than comfortable loudness
Laboratory
 Part II: The Lx wave (cont.)
Fill in table with F0’s from the sample
# of cycles/total time x 1000= F0 (Hz)
if it looks like 1/2 a cycle count as such (3.5, 5.5 etc.)
Fill in the table with open % and contact %
Compare different pitch and loudness
levels(amplitude, frequency of waveform and vocal
contact time)
Laboratory
Part III: Lx and Vocal Register
Use Figure A:
Modal register
Pulse
Falsetto
Calculate F0 of each
Characteristics of each register
Laboratory
Part IV: Lx and vocal disorder
Use Figure B:
Mark any strange characteristics of this
waveform
What can you say about this waveform in
comparison to normal voices?