Electroglottography:  laryngography EEG, represents relative contact area of the vf
A high-frequency signal of very low current is generated and passed through two surface electrodes held in place with a Velcro band at either side of the person’s thyroid cartilage.  Because tissue is a good conductor of electricity and air is not, when the vf are closed the current passes easily from one electrode to the other (resistance is low).  When open resistance is greater.  The changing of resistance as the vf open and close is displayed on a screen as a waveform.  The Lx wave reflects the surface area of contact of the vf. As the vf close during vibration the resistance to the electrical current decreases and the amplitude of the wave increases so the Lx produces a record of vf vibration during phonation.

What’s the difference between an acoustic waveform and a Lx waveform.  The acoustic waveform is measuring air pressure differences which corresponds to the the opening and closing of the vf.  The Lx reflects the duty cycle of the vf (phase of vf vibratory cycle: opening, open, closing, closed

Be able to describe figure 6.14.

What does counting the peaks in a Lx waveform tell you? Fo cycles per second
What does a reduced number of cycles per second indicate? using pulse register
What does greater number of cycles per second indicate?  Falsetto.
What does a longer than normal closed time tell you? Hyperfuncitoning
What does an irregular pattern of cycles in the waveform tell you? Aperiodic vibration (hoarseness)
What does modal register Lx waveform look like?  Closing phase has a steeper slope than the opening phase (elastic recoil is faster than pressure buildup)
What does pulse register Lx waveform look like?   Shows more than one peak per cycle (bi/multiphasic closure pattern), sharp short pulses (multiphasic closure) followed by a long closed glottal interval, fewer cycles/s
Be able to identify the Lx in 6.15

What are the EGG slope quotients what can they tell you, and how are they obtained?
Based on the duty cycle and the various proportions of time that each phase takes to complete.  They indicate vf behavior during vf contact.

Closed quotients: CP(closed phase)/P(period)
Degree of medial compression being exerted.  Norm .50-.06
Compares the duration of the closed phase to the time of the entire vibratory cycle.  Higher CQ indicates longer duration of closure: hyperfunctioning of vf (loud, tense), lower CQ reflects shorter closure duration: hypofunctioning of vf(breathy, or falsetto).

Contact index: CP-OP/CP (closing and opening/closed)  ratio of the difference in time between the closing and opening phases divided by the duration of the closed phase.  It is sensitive to the mucosal wave of the vf covers providing information about the way in which the vf are vibrating in a particular register.
 
Closed to open ratio (CP/CO) (closed/open phase)relative duration of the closed and open phases of the duty cycle.  How long the vf are closed compared to how long they are open (hyper- hypofunctioning) A longer closed phase results in a higher C/O, lower C/P indicates a shorter closed phase