The fundamental frequency is measured by the strobe unit and used to set the frequency of the light flashes. An identical frequency is emitted in the locked mode that produces a still image of a single portion of the vibratory cycle. The periodicity refers to the regularity of successive vocal motions. Normal vibratory activity is regular and periodic. Amplitude refers to the lateral excursion of the vocal folds during their displacement away from the midline in oscillation.
Typical amplitude is approximately one third of the total width of the vocal fold.
Amplitude generally is graded as normal, less than normal, or greater than normal. Normal motion of the vocal folds is symmetric, both in vibratory characteristic and in adductory and abductory motion. The pattern of light traveling from medial to lateral along the superior surface of the vocal fold during vibration under illumination is referred to as the mucosal wave. Focal abnormalities of mucosal wave help to localize pathology within the vocal fold. By increasing the illumination and evaluation of vibratory patterns, videostroboscopy has vastly increased the sensitivity of laryngological diagnoses.