The increase of glottal resistance is the main mechanism to increase vocal intensity at low fundamental frequency. This increase is due to adductory forces provoked by the contraction of intrinsic laryngeal muscles that increases tension and approximates the vocal folds to the midline. However, the same behavior can be observed in functional disorders, like adductor spasmodic dysphonia and hyperfunctional dysphonia, even during soft phonation. AIM: To evaluate the vibratory pattern of the vocal folds in subjects with normal voice according to intensity variation, in order to establish standard values for the vibratory cycle phases. These values may improve the diagnosis and the follow up of those disorders. STUDY DESIGN: Clinical prospective. SUBJECTS AND METHODS: Fifty-eight adults were evaluated during habitual (soft) and loud phonation. Vocal folds vibration patterns were analyzed with videokymography. Vocal intensity variation was studied with acoustic analysis software, comparing the intensity levels during habitual phonation and loud phonation. RESULTS: The results showed a spontaneous fundamental frequency (F0) rise as vocal intensity grew and a decrease of the open quotient at loud intensity phonation. CONCLUSION: Sound intensity levels were established at habitual (63,46 dB) and loud phonation (72,55dB). Open quotient (OQ) values were also established for those intensity phonation levels.
vocal folds; kymography; vibration; voice acoustic
